• Title, Summary, Keyword: aluminum trihydroxide

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Mixed Grinding Effect on Kaolinite-Aluminum Trihydroxide Mixture and Its Influence on Mullite Formation (Kaolinite-Aluminum Trihydroxide의 혼합물의 혼합분쇄효과 및 Mullite의 생성에 미치는 영향)

  • 류호진
    • Journal of the Korean Ceramic Society
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    • v.34 no.2
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    • pp.195-201
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    • 1997
  • The present paper describes the effect of dry mixed grinding on kaolinite-aluminum trihydroxide mixture with a planetary ball mill before sintering and its influence on mullite formation during sintering. The size reduction of the mixture is market in the early stage of grinding and the obtained fine particles agglomerate subsequently with an increase of grinding time. The crystal structure of the mixture is collapsed easily into an amorphous one by planetary ball milling, of which amount increases with an increase of grinding time. Only mullite phase except for anatase as an inherent impurity in kaolinite appeared in the sintered body of the mixtures with mixed grinding as relatively lower temperature 1523K, while corundum, cristobalite, and Al-Si spinel phases, besides mullite were formed in the sintered body of the mixture without mixed grinding. Therefore, the mixed grinding treatment is very effective to improve the homogeneous mixing and disp-ersion of the mixture of raw materials on a micro scale and to decrease the thermal decomposition tem-perature by crystal structure change of them so as to obatin direct preparation of mullite with high purity at relatively low temperature.

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Flame Retardancy and Thermal Properties of PVC/ATH Composites Prepared by a Modular Intermeshing Co-rotating Twin Screw Extruder

  • Lee, Hyeongsu;Park, Se-Ho;Lee, Jae-Yeul;Park, Yuri;Jeong, Hobin;Jhee, Kwang-Hwan;Bang, Daesuk
    • Elastomers and Composites
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    • v.51 no.2
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    • pp.147-153
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    • 2016
  • Polyvinyl chloride (PVC) has been used as a general-purpose polymer because of its lower cost, good durability and mechanical properties compared to other materials. However, PVC is vulnerable to heat deformation and generates a toxic gas like hydrogen chloride. Therefore, it is important to delay or prevent the flame retardancy and thermal degradation of the PVC during the processing. It was reported that aluminum trihydroxide (ATH) improved flame retardancy as well as smoke inhibition of the virgin polymer. In this study, PVC composites by addition of ATH were compounded in a modular intermeshing co-rotating twin screw extruder. The PVC composites with different concentrations of ATH (0~5 phr) were analyzed. Flame retardancy of the PVC composite significantly increased depending on the ATH concentration. LOI of the composite also increased with the concentration of ATH. There were no significant differences for the thermal properties of the PVC composites with ATH.

Flame Retardancy and Physical Properties of Ethylene Vinyl Acetate/Aluminum Trihydroxide Composites (에틸렌 비닐아세테이트/수산화알루미늄 복합재료의 난연 및 물리적 특성)

  • Lee, Minho;Yu, Dayeong;Kim, Yeongho;Lee, Sunghee;Kim, Jeong Ho;Lee, Young Chul
    • Polymer(Korea)
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    • v.39 no.3
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    • pp.433-440
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    • 2015
  • Aluminum trihydroxide (ATH) has been commonly employed as a flame retardant for ethylene vinyl acetate (EVA) copolymers. In the present work, ATH was obtained from a recycling process of multi-layer packaging film wastes. EVA/ATH composite samples were prepared using a two roll-mill and flame retardancy of EVA/ATH composites were examined using limiting oxygen index (LOI) and flame retardancy test (UL94). We observed excellent flame retardancy in case of adding 150 phr or more of recycled ATH to EVA. Particle size and specific surface area play crucial roles in LOI value and UL-94 classification of the EVA/ATH composites. Smaller particle size and higher specific surface area of ATH was found out to improve the flame retardancy. Regarding tensile properties, crosslinked EVA/ATH compounds which is practically used for electric cables had similar to or even better tensile property values than the ones without ATH.

The Rehydration Properties of Amorphous Alumina Powder in Low Water/Alumina Ratio (낮은물/알루미나 비에서 비정질 알루미나 분말의 수화특성)

  • 박병기;서정권;이정민;서동수
    • Journal of the Korean Ceramic Society
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    • v.35 no.10
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    • pp.1085-1093
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    • 1998
  • Amorphous alumina powder prepared by the fast calcination of aluminum trihydroxide(Al(OH)3 gibbsite) for 0.5 second at 580$^{\circ}C$ was investigated rehydration propeties. Phase composition crystal size and mor-phology surface area pore volume and pore size distribution of pesudo-boehmite and bayerite crystals changed with temperature time water/alumina ratio and particle size when amorphous alumina rehydrated with water. Phase compositions were examined with XRD and DTA and crystal sized morphologies were investigaed with SEM and TEM. Also rehydration properties of amorphous alumina were in-vestigated by measuring the surface area pore volume and pore size distribution.

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Characteristics of $\gamma$-Alumina Prepared from Rehydrated Amorphous Alumina (수화한 무정형 알루미나로부터 제조된 $\gamma$-Alumina의 특성)

  • Kim, Yun-Seop;Go, Hyeong-Sin;Seo, Jeong-Gwon;Lee, Jeong-Min;Ha, Baek-Hyeon
    • Korean Journal of Materials Research
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    • v.11 no.11
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    • pp.978-985
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    • 2001
  • The amorphous alumina was obtained by flash calcination of Bayer gibbsite[$Al(OH)_3$aluminum trihydroxide]. Rehydration and pore characteristics of $r-A1_2O_3$ prepared from rehydrated amorphous alumina were investigated. Crystal phases of pseudo-boehmite and bayerite were changed when amorphous alumina was hydrated at various conditions such as time, the ratio of water/alumina and pH. Specific surface areas and pore volumes of $r- A1_{2O}_3$ were influenced by the reaction time, water/alumina and PH of rehydration. The total pore volume of $r-A1_{2O}_3$increases with increasing the reaction time and ratio of water/alumina. Especially, the pure pseudo-boehmite of single phase could be prepared, when amorphous alumina was hydrated in the range of pH 6.5-8.0 in water/alumina= 10 at $90^{\circ}C$ for 7hr. The $r-Al_{2O}_3$, obtained by calcination of the prepared pseudo-boehmite at $500^{\circ}C$ for 2hrs, is characterized by the specific surface area of $265m^2$/g, total pore volume of $0.75cm^3$/g.

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Imaging Plate Technique for the Electron Diffraction Study of a Radiation-sensitive Material under Electron Beam (전자 빔 조사 민감 물질의 전자회절분석을 위한 Imaging Plate 기술)

  • Kim, Young-Min;Kim, Yang-Soo;Kim, Jin-Gyu;Lee, Jeong-Yong;Kim, Youn-Joong
    • Applied Microscopy
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    • v.38 no.3
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    • pp.185-193
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    • 2008
  • An experimental comparison of the detection properties between imaging plate and film for recording the electron diffraction pattern was carried out on a radiation-sensitive material, an aluminum trihydroxide(gibbsite, ${\gamma}-Al(OH)_3$), through the electron beam irradiation. Because the imaging plate has a wide dynamic range sufficient for recording extremely low- and high-electron intensities, the range of spatial frequency for the diffraction pattern acquired by the imaging plate was extended to two times larger than the range by the film, especially at a low electron dose condition(${\leq}0.1\;e^-/{\mu}m^2$). It is also demonstrated that the imaging plate showed better resolving power for discriminating fine intensity levels even in saturated transmitted beam. Hence, in the respect of investigating the structures of radiation-sensitive materials and cryo-biological specimens, our experimental demonstrations suggest that the imaging plate technique may be a good choice for those studies, which have to use an extremely low electron intensity for recording.