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이정아,김정주 한국세라믹학회 1999 한국세라믹학회지 Vol.36 No.7
Densification and grain growth behavior of bimodal size distributed alumina powder mixtures were investigated as a function of amount of coarse alumina powder. The specimens which contained coarse alumina powder for 60to 80wt% showed the highest green density. The amount of shrinkage of sintered specimen lineraly decreased with the increase of coarse alumina powder up to the content that showed the highest green density and then further addition of coarse alumina powder led to drastic decrease of shrinkage of specimen. Especially crack-like void were concurrently revealed in the sintered body with addition of coarse alumina powder above 60wt% When the sintering temperature increased up to 1650$^{\circ}C$ the amount of shrinkage of specimen linearly decreased and the grain growth were also retarded with increase of coarse lauminia powder.
Making Alumina Microcomponents from Al Powder
Kim J.S.,Jiang K.,Falticeanu L.,Daviesd G.J.,Chang I. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Alumina microcomponents have distinguishing advantages over Si counterpart. However, the shrinkage of alumina, as high as 20%, makes it difficult to produce precision components meeting a high tolerance. A new fabrication process presented to greatly reduce the shrinkage by producing alumina microcomponents from ultrafine Al powder. The process consists of forming Al powder components through sintering and turning the Al powder component into alumina. In this way, the shrinkage occurring in sintering the Al powder component will be compensated by the expansion appearing when the Al powder component turns into alumina. The process has proven successful.
Kim, Ji-Soon,Kim, H. T.,Illyin, A. P.,Kwon, Young-Soon The Korean Powder Metallurgy Institute 2005 한국분말재료학회지 (KPMI) Vol.12 No.5
Nanoscale Al powder with thin layer of alumina was produced by Wire Electric Explosion (WEE) process. Spark-Plasma Sintering (SPS) was performed for the produced powder to confirm the effectiveness of SPS like so-called 'surface-cleaning effect' and so on. Crystallite size and alumina content of produced powder varied with the ratio of input energy to sublimation energy of Al wire ($e/e_s$): Increase in ($e/e_s$) resulted in the decrease of crystallite size and the increase of alumina content. Shrinkage curve during SPS process showed that the oxide surface layer could not be destroyed near the melting point of Al. It implied that there was not enough or no spark-plasma effect during SPS for Al/Alumina powder.
보헤마이트로부터 $\alpha$-알루미나 분말 제조시 분말 물성에 미치는 음이온의 영향
임경란,임창섭,장진욱 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.8
boehmite which is the by-product in alcohol process contains anions such as $Cl^-,{NO_3}^-.or\; CH_3COO^-$ Influe-nce of these anions was studied on properties of $\alpha$-alumina powders prepared by treating the transformed ${\gamma}$-alumina with the alumina sol and $\alpha$-alumina seeds (d_{50}=0.36\mu\textrm{m}$) Disperal 20/1 and 10/1 containing $Cl^-$ produced spherical powder Disperal 20/2 with ${NO_3}^-$ produced equiaxed powder and Disperal 10/3 with $CH_3$ $COO^-$ irregular shaped and sized powder. All of these $\alpha$-alumina powders were submicron. Although the green density of the alumina powder derived from Disperal 10/1 by calcination at $1200^{\circ}C$/1h. was 53% it did not sinter even at $1550^{\circ}C$ for 2h. which implies that its d50 is greater than $3\mu\textrm{m}$. The others gave green densities in the range of 44~47% but they sintered as well as the AKP-30 at $1500^{\circ}C$/2 h or $1550^{\circ}C$/2 h.
분말사출성형 시 분말 혼합체의 유동성 시뮬레이션을 통한 투광성 알루미나 소결체의 특성 연구
김형수,변종민,김세훈,김영도,Kim, Hyung Soo,Byun, Jong Min,Kim, Se Hoon,Kim, Young Do 한국분말야금학회 2014 한국분말재료학회지 (KPMI) Vol.21 No.3
Translucent alumina is a potential candidate for high temperature application as a replacement of the glass or polymer. Recently, due to the increasing demand of high power light emitting diode (LED), there is a growing interest in the translucent alumina. Since the translucent property is very sensitive to the internal defect, such as voids inside or abnormal grain growth of sintered alumina, it is important to fabricate the defect-free product through the fabrication process. Powder injection molding (PIM) has been commonly applied for the fabrication of complex shaped products. Among the many parameters of PIM, the flowability of powder/binder mixture becomes more significant especially for the shape of the cavity with thin thickness. Two different positions of the gate were applied during PIM using the disc type of die. The binder was removed by solvent extraction method and the brown compact was sintered at $1750^{\circ}C$ for 3 hours in a vacuum. The flowability was also simulated using moldflow (MPI 6.0) with two different types of gate. The effect of the flowability of powder/binder mixture on the microstructure of the sintered specimen was studied with the analysis of the simulation result.
가수분해법에 의한 알루미나 코팅 지르코니아 분말의 제조
이종국,김윤수,김환,Lee, Jong-Kook,Kim, Yoon-Soo,Kim, Hwan 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.12
Zirconia powder coated with alumina was prepared by hydrolysis of alumina butoxide. The coated powder was obtained by a hydrolysis reaction between the adsorbed water on the surface of zirconia particles and aluminum sec-butoxide. Amorphous aluminum hydroxide was uniformly coated on the surface of zirconia particles with the thickness of about 30 nm. The shape and distribution of aluminum hydroxide was varied with an existence of surfactant. The coated layer of aluminum hydroxide consists of the fine particle size, and the zirconia powder coated by alumina hydroxide have the large specific surface area of 120 $m^2$/g, compared with that of starting zirconia powder.
Jilin Hu,Xiuying Tian,Chuanyue Hu,Yige Luo,Hongxia Peng,Jinqiu Luo 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.11
Different types of aluminum sources (such as Al2O3 and Al(OH)3) were used to prepare an Al2O3-ZrO2 composite powder inan alcohol-water system, in which ZrOCl2·8H2O and NH4HCO3 were used as starting material and precipitant, respectively. This study explores the effects of different types of aluminum sources and heat treatment on the preparation of Al2O3-ZrO2composite powder. The sintering property of the Al2O3-ZrO2 composite powder prepared from different types of aluminumsources was also investigated. Results indicate that Al2O3-ZrO2 composite powder prepared from Al(OH)3-containingprecursors after calcination at 600 oC possesses a relatively uniform spherical structure, with particle size ranging from 50 nmto 100 nm. As the calcination temperature increases, the particle size of powder prepared using precursors that containAl(OH)3 increases and the micro appearance of the particles gradually shifts from a mainly spherical structure to a diversifiedstructure, which can be spherical, sheet-like or rod-like. The Al2O3-ZrO2 composite powder prepared from Al(OH)3-containingprecursors exhibits satisfactory sintering property. The relative density of the sintered sample reaches 98.5%, and the Rockwellhardness reaches 85.5 HRA after sintering of the composite powder at 1550 oC for 2 hrs
폴리머용액법 및 알루미나 seed를 도입한 YAG:Ce<sup>3+</sup> 형광체 분말 합성
김용현,이상진,Kim, Yong-Hyeon,Lee, Sang-Jin 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.1
$YAG:Ce^{3+}$ phosphor powders were synthesized using a $Al_2O_3$ seed (average particle size: 5 ${\mu}m$) by the polymer solution route. PVA solution was added to the sol precursors consisting of the seed powder and metal nitrate salts for homogeneous mixing in atomic scale. All dried precursor gels were calcined at $500^{\circ}C$ and then heated at $1400^{\circ}C{\sim}1500^{\circ}C$ in $N_2/H_2$ atmosphere. The final powders were characterized by using XRD, SEM, PSA, PL and PKG test. All synthesized powders were crystallized to YAG phase without intermediate phases of YAM or YAP. The phosphor properties and morphologies of the synthesized powders were strongly dependent on the PVA content. Finally, the synthesized $YAG:Ce^{3+}$ phosphor powder heated at $1500^{\circ}C$, which is prepared from 12:1 PVA content and has an average particle size of 15 ${\mu}m$, showed similar phosphor properties to a commercial phosphor powder.
셀레늄과 세라믹 혼합분말을 사용한 Cu<SUB>0.9</SUB>In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>Se₂ 분말층의 소결거동 연구
송봉근(Bong-Geun Song),황윤정(Yoonjung Hwang),박보인(Bo-In Park),이승용(Seung Yong Lee),이재승(Jae-Seung Lee),박종구(Jong-Ku Park),이도권(Doh-Kwon Lee),조소혜(So-Hye Cho) 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.3
Cu(In,Ga)Se₂ (CIGS) thin films have been used as a light absorbing layer in high-efficiency solar cells. In order to improve the quality of the CIGS thin film, often selenization step is applied. Especially when the thin film was formed by non-vacuum powder process, selenization can help to induce grain growth of powder and densification of the thin film. However, selenization is not trivial. It requires either the use of toxic gas, H₂Se, or expensive equipment which raises the overall manufacturing cost. Herein, we would like to deliver a new, simple method for selenization. In this method, instead of using a costly two-zone furnace, use of a regular tube furnace is required and selenium is supplied by a mixture of selenium and ceramic powder such as alumina. By adjusting the ratio of selenium vs. alumina powder, selenium vaporization can be carefully controlled. Under the optimized condition, steady supply of selenium vapor was possible which was evidently shown by large grain growth of CIGS within a thin powder layer.
셀레늄과 세라믹 혼합분말을 사용한 Cu<sub>0.9</sub>In<sub>0.7</sub>Ga<sub>0.3</sub>Se<sub>2</sub> 분말층의 소결거동 연구
송봉근,황윤정,박보인,이승용,이재승,박종구,이도권,조소혜,Song, Bong-Geun,Hwang, Yoonjung,Park, Bo-In,Lee, Seung Yong,Lee, Jae-Seung,Park, Jong-Ku,Lee, Doh-Kwon,Cho, So-Hye 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.3
$Cu(In,Ga)Se_2$ (CIGS) thin films have been used as a light absorbing layer in high-efficiency solar cells. In order to improve the quality of the CIGS thin film, often selenization step is applied. Especially when the thin film was formed by non-vacuum powder process, selenization can help to induce grain growth of powder and densification of the thin film. However, selenization is not trivial. It requires either the use of toxic gas, $H_2Se$, or expensive equipment which raises the overall manufacturing cost. Herein, we would like to deliver a new, simple method for selenization. In this method, instead of using a costly two-zone furnace, use of a regular tube furnace is required and selenium is supplied by a mixture of selenium and ceramic powder such as alumina. By adjusting the ratio of selenium vs. alumina powder, selenium vaporization can be carefully controlled. Under the optimized condition, steady supply of selenium vapor was possible which was evidently shown by large grain growth of CIGS within a thin powder layer.