• 제목/요약/키워드: Porous alumina

검색결과 214건 처리시간 0.026초

Optimization for Permeability and Electrical Resistance of Porous Alumina-Based Ceramics

  • Kim, Jae;Ha, Jang-Hoon;Lee, Jongman;Song, In-Hyuck
    • 한국세라믹학회지
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    • 제53권5호
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    • pp.548-556
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    • 2016
  • Recently, porous alumina-based ceramics have been extensively applied in the semi-conductor and display industries, because of their high mechanical strength, high chemical resistance, and high thermal resistance. However, the high electrical resistance of alumina-based ceramics has a negative effect in many applications due to the generation of static electricity. The low electrical resistance and high air permeability are key aspects in using porous alumina-based ceramics as vacuum chucks in the semi-conductor industry. In this study, we tailored the pore structure of porous alumina-based ceramics by adjusting the mixing ratio of the starting alumina, which has different particle sizes. And the electrical resistance was controlled by using chemical additives. The characteristics of the specimens were studied using scanning electron microscopy, mercury porosimetry, capillary flow porosimetry, a universal testing machine, X-ray diffraction, and a high-resistance meter.

Electrochemical Synthesis of TiO2 Photocatalyst with Anodic Porous Alumina

  • Hattori, Takanori;Fujino, Takayoshi;Ito, Seishiro
    • 한국재료학회지
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    • 제17권11호
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    • pp.593-600
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    • 2007
  • Aluminum was anodized in a $H_2SO_4$ solution, and titanium (IV) oxide ($TiO_2$) was electrodeposited into nanopores of anodic porous alumina in a mixed solution of $TiOSO_4$ and $(COOH)_2$. The photocatalytic activity of the prepared film was analyzed for photodegradation of methylene blue aqueous solution. Consequently, we found it was possible to electrodeposit $TiO_2$ onto anodic porous alumina, and synthesized it into the nanopores by hydrolysis of a titanium complex ion under AC 8-9 V when film thickness was about $15-20{\mu}m$. The photocatalytic activity of $TiO_2$-loaded anodic porous alumina ($TiO_2/Al_2O_3$) at an impressed voltage of 9 V was the highest in every condition, being about 12 times as high as sol-gel $TiO_2$ on anodic porous alumina. The results revealed that anodic porous alumina is effective as a substrate for photocatalytic film and that high-activity $TiO_2$ film can be prepared at low cost.

Indentation Damage of Porous Alumina Ceramice

  • Ha, Jang-Hoon;Lee, Chul-Seung;Kim, Jong-Ho;Kim, Do-Kyung
    • 한국세라믹학회지
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    • 제41권1호
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    • pp.19-23
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    • 2004
  • The Hertzian indentation contact damage behavior of porous alumina with controlled pore shape was investigated by experiments. Porous alumina ceramics containing well-defined pore shape, size and distribution were prepared by incorporation of fugitive spherical starch. Porous alumina with isolated pore structure was prepared with porosity range up to 30%. The indentation stress-strain curves of porous alumina were constructed. Elastic modulus and yield stress can be obtained from the stress-strain relationship. Impulse excitation method for the measurement of elastic modulus was also conducted as well as Hertzian indentation and was confirmed as a useful tool to evaluate the elasticity of highly porous ceramics. Elastic modulus of the inter-connected pore structure is more sensitive to porosity than that of the isolated pore structure. When the specimen had isolated pore structure, higher yield point was obtained than it had inter-connected pore structure. This study proposed that the elastic modiulus of porous ceramics is strongly related to not only porosity, but also the structure of pore.

Viscosity Study to Optimize a Slurry of Alumina Mixed with Hollow Microspheres

  • Bukhari, Syed Zaighum Abbas;Ha, Jang-Hoon;Lee, Jongman;Song, In-Hyuck
    • 한국세라믹학회지
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    • 제52권6호
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    • pp.403-409
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    • 2015
  • Porous alumina ceramics are involved in many industrial applications due to the exceptional properties of these products. This study addresses the preparation of porous alumina ceramics using hollow microspheres as a pore-forming agent and slip casting as a green-body-forming technique. A uniform distribution of pores is a basic requirement of a porous material. This study investigates three different slurry systems, i.e., as-prepared alumina slurry, alumina slurry electrostatically dispersed by hydrochloric acid (HCl), and slurry dispersed by the commercial dispersant 'Darvan C-N'. At a low viscosity, the hollow microspheres in the slurry tend to float, which causes a non-uniform pore distribution. To avoid this phenomenon, the viscosity of the slurry was increased to the extent that the movement of hollow microspheres ceased in the slurry. As a result, a uniform pore distribution was achieved.

Boehmite 수화졸의 알루미나로 제조한 다공성 알루미나 세라믹스의 기공특성 (Pore Characteristics of Porous Alumina Ceramics Fabricated from Boehmite Hydrosol and Alumina Particles)

  • 오경영
    • 한국세라믹학회지
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    • 제33권5호
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    • pp.547-555
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    • 1996
  • Porous alumina ceramics were fabricated by pseudo-boehmite phydosol-gel process within/without commercial $\alpha$-alumina particles average 1 and 40 micron respectively. The pore characteristics of fired specimens were studied by the measurement of bulk density total porosity thyermal analysis pore volume pore distribution BET area XRD and SEM. with increasing of firing temperature pore volume and BET surface area were decreased and the average pore size was increased to approximately 146$\AA$ upto 80$0^{\circ}C$ by de-watering of [OH] and formation of $\alpha$-alumina. The fired relative density of the alumina-dispersed specimen with average 1 micron particle was increased with the amounts of dispersed particle by bimodal packing theory which is compared to the ones of specimen including of average 40 micron particle. It was confirmed that the percola-tion threshold in porous ceramics with coarser particle (40 micron) has formed between the transformed-alumina from hydrogel and dispersed-alumina of above 50 vol% particle and the total porosity was increased at the threshold point above.

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나노 기공성 알루미나의 생성과 화학적 용해 거동 (Formation and Chemical Dissolution Behaviors of Nano Porous Alumina)

  • 오한준;정용수;지충수
    • 한국표면공학회지
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    • 제43권5호
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    • pp.217-223
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    • 2010
  • For an application as templates of high performance with proper pore size and shape, porous anodic alumina films were prepared by anodization in oxalic acid, and formation behaviors of anodic alumina layer as well as dissolution process in acid solution have been investigated. The surface characteristics on anodic alumina layer were shown to be dependent on the fabrication parameters for anodization. For the dissolution behaviors of anodic alumina, the thickness of the barrier-type alumina layer decreased linearly with the rate of 0.98 nm/min in $H_3PO_4$ solution at $30^{\circ}C$. The changes of the anodic alumina layers were analyzed by SEM and TEM.

Thermally Stabilized Porous Nickel Support of Palladium Based Alloy Membrane for High Temperature Hydrogen Separation

  • Ryi, Shin-Kun;Park, Jong-Soo;Cho, Sung-Ho;Hwang, Kyong-Ran;Kim, Sung-Hyun
    • Corrosion Science and Technology
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    • 제6권3호
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    • pp.133-139
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    • 2007
  • Nickel powder was coated with aluminum nitrate solution to increase the thermal stability of a porous nickel support and control the nickel content in the Pd-Cu-Ni ternary alloyed membrane. Raw nickel powder and alumina coated nickel powder were uniaxialy pressed by home made press with metal cylindrical mold. Though the used nickel powder prepared by pulsed wire evaporation (PWE) method has a good thermal stability, the porous nickel support was too much sintered and the pores of porous nickel support was plugged at high temperature (over $800^{\circ}C$) making it not suitable for the porous support of a palladium based composite membrane. In order to overcome this problem, the nickel powder was coated by alumina and alumina modified porous nickel support resists up to $1000^{\circ}C$ without pore destruction. Furthermore, the compositions of Pd-Cu-Ni ternary alloy membrane prepared by magnetron sputtering and Cu-reflow could be controlled by not only Cu-reflow temperature but also alumina coating amount. SEM analysis and mercury porosimeter analysis evidenced that the alumina coated on the surface of nickel powder interrupted nickel sintering.

무가압분말충전성형법에 의한 다공성 세라믹스의 제조 및 특성 : I. 알루미나 (The Fabrication and Characteristics of Porous Alumina Ceramics by Pressureless Powder Packing Forming Method : I . Alumina)

  • 박정현;황명익;김동희;최환욱;김용남
    • 한국세라믹학회지
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    • 제36권6호
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    • pp.662-670
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    • 1999
  • Porous alumina was fabricated from pressureless powder packing forming method using powders granulated by spray drying. It was investigated the pore size distribution of fabricated porous alumina. The results of microstructural observation showed that intraganular pore size and intragranular pore size. At 1700$^{\circ}C$ there were no intragranular pores but it showed homogeneous distribution of intergranular pore size. The bending strength and shrinkage increased as porosity decreased. In case of thermal shock resistance sudden decrease of bending strength to $\Delta$T was not shown because intergranular large pore prevented sudden crack propagation.

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다중압출공정을 이용한 알루미나 연속다공질체 제조 및 그의 생체친화성 평가를 위한 In-vitro, In-vivo 실험 (Fabrication of Continuously Porous Alumina Bodies by Multi-Extrusion Process and their In-vitro and In-vivo Study for Biocompatibility)

  • 강인철;조순희;송호연;이병택
    • 한국세라믹학회지
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    • 제41권7호
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    • pp.560-566
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    • 2004
  • 다중 압출 공정을 이용하여 알루미나 연속다공질체를 제조하기 위해 기공형성제로서 탄소 분말을 사용하였으며 세라믹 분말의 성형을 용이하게 하기 위하여 에틸렌 비닐 아세테이트 고분자를 바인더로 사용하였다. 압출 횟수, 압출비 및 재료의 부피비를 제어함으로써 균일한 기공의 크기와 기공률을 용이하게 제어하였다. 제조된 소결체는 연속기공을 가질 뿐아니라 우수한 비표면적을 가졌으며, 기존의 공정에 의해 제조된 알루미나 다공질 재료보다 우수한 곡강도 값을 보였다. 생체 친화성 평가를 위해 인간의 뼈모세포인 MG-63 세포를 이용해 In-vitro 실험을 실시한 결과 기공의 아랫면, 윗면, 내부 및 외부에 세포가 잘 생착하여 네트워크 형태로 치밀하게 잘 성장하였다. 또한 이 재료를 이용하여 3차원 다공질체로 제조한 후 생체적합성을 평가하기 위해 쥐의 피하조직에 이식한 결과 어떠한 염증 소견이나 생체 거부반응이 없었으며 섬유조직으로 잘 둘러 쌓인 다공질체 주위로 새로운 모세혈관이 활발히 생성되었다.

The Effect of MnO2 Content on the Permeability and Electrical Resistance of Porous Alumina-Based Ceramics

  • Kim, Jae;Ha, Jang-Hoon;Lee, Jongman;Song, In-Hyuck
    • 한국세라믹학회지
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    • 제54권4호
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    • pp.331-339
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    • 2017
  • Porous alumina-based ceramics are of special interest due to their outstanding mechanical properties and their thermal and chemical stability. Nevertheless, the high electrical resistance of alumina-based ceramics, due to the generation of static electricity, leads to difficulty in applying a vacuum chuck in the semi-conductor process. Therefore, development of alumina-based ceramics for applications with vacuum chucks aims to have primary properties of low electrical resistance and high air permeability. In this study, we tailored the electrical resistance of porous alumina-based ceramics by adjusting the amount of $MnO_2$ (with $TiO_2$ fixed at an amount of 2 wt%) and by using coarse alumina powder for high air permeability. The characteristics of the specimens were studied using scanning electron microscopy, mercury porosimeter, capillary flow porosimetry, universal testing machine, X-ray diffraction and high-resistance meter.