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RISS 인기검색어
- 검색키워드
- 저자 : Heberto Balmori Ram?rez (검색결과 5 건)
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Richard C. Bradt,Heberto Balmori-Ramirez,Joaquin Aguilar-Santillan 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.3
The sol-gel formation of Bayerite, Al(OH)3, precipitated from AlCl3·6H2O (13.6 g/l) and NH4OH (4N) at a basic pH 9 was studied. The resulting Bayerite was in the form of prisms ~3 µm in length. The transformation of this Bayerite to α-alumina was [Al(OH)3 ] → γ-Al2O3 → δ-Al2O3 → θ-Al2O3 → α- Al2O3. The slowest of these transitions, the one which controls the transformation by nucleation and growth kinetics, is the θ-Al2O3 to α-Al2O3. This rate-controlling transformation was studied by two different thermal treatments. One was isothermal and the other had two steps, the first of which created “in situ” nuclei, to enhance the transformation rate. The latter treatment reduced the time for the transformation at 1100oC from >80 h to only ~13 h and reduced the activation energy from 419.02 kJ mol−1 to 317.52 kJ mol−1. It produced a finer crystal size of α-alumina.
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Dense mullite from attrition milled kyanite and α-alumina
Joaquin Aguilar-Santillan,Heberto Balmori-Ramirez,Richard C. Bradt 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.1
Effects of attrition milling on the decomposition of kyanite (Al2SiO5) and its reaction with α-alumina (Al2O3) to form stoichiometric mullite (3Al2O3·2SiO2) are reported. Kyanite-alumina mixes were attrition milled for times from 1 h to 12 h. With increasing milling time, the kyanite decomposition was accelerated and secondary mullite formation from the reaction between the rejected silica and the added alumina was enhanced. Milling reduced the decomposition expansion from +15.0% to +0.1% and the final contraction or densification from +2.5% to −13.7%. During firing complete mullite formation occurred after firing at only 1623 K/1h (1350oC/1 h) to produce a dense mullite ceramic with a fine grain size (~1 μm). Effects of attrition milling on the decomposition of kyanite (Al2SiO5) and its reaction with α-alumina (Al2O3) to form stoichiometric mullite (3Al2O3·2SiO2) are reported. Kyanite-alumina mixes were attrition milled for times from 1 h to 12 h. With increasing milling time, the kyanite decomposition was accelerated and secondary mullite formation from the reaction between the rejected silica and the added alumina was enhanced. Milling reduced the decomposition expansion from +15.0% to +0.1% and the final contraction or densification from +2.5% to −13.7%. During firing complete mullite formation occurred after firing at only 1623 K/1h (1350oC/1 h) to produce a dense mullite ceramic with a fine grain size (~1 μm).
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Preparation and characterization of TiN powder by reactive milling in air
Joaquina Orea-Lara,Heberto Balmori-Ramírez,F. J. de Anda-Salazar,H. Yee-Madeira 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.1
TiN powder was obtained by the reactive milling of a titanium powder in an air atmosphere, utilizing an attrition mill. Characterization of the powders was carried out by means of chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The reaction took place over a period of 96 hours in the attrition mill. The XRD results indicate that a cubic TiN-like phase crystalline structure was produced in the mill, with a lattice parameter of 4.38 Å. The morphology of the obtained powders was nodular, having particle sizes within the nanometric size range. TiN powder was obtained by the reactive milling of a titanium powder in an air atmosphere, utilizing an attrition mill. Characterization of the powders was carried out by means of chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The reaction took place over a period of 96 hours in the attrition mill. The XRD results indicate that a cubic TiN-like phase crystalline structure was produced in the mill, with a lattice parameter of 4.38 Å. The morphology of the obtained powders was nodular, having particle sizes within the nanometric size range.
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Nano-milling of the sillimanite mineral, kyanite, and its reactions with alumina to form mullite
Richard C. Bradt,Joaquin Aguilar-Santillan,Heberto Balmori-Ramirez 한양대학교 세라믹연구소 2005 Journal of Ceramic Processing Research Vol.6 No.4
The sillimanite group of minerals, kyanite, andalusite and sillimanite, the three polymorphs of Al2SiO4, is a natural raw material for the production of mullite in many traditional ceramics. However, the sillimanites form at high pressures and are alumina-deficient relative to mullite. This paper addresses the effects of attrition milling kyanite, the most common of the three to the nanoscale. Additions of aluminum metal, that is then oxidized to alumina and an independent addition of pure alumina to yield a phase-pure mullite after firing, are also described. The attrition milling size reduction of natural kyanite to the nanoscale has several pronounced beneficial effects. It reduces the phase decomposition temperature, it eliminates the large volume expansion of the decomposition and it produces a highly reactive form of the rejected silica. When fired with alumina additions adjusted to the mullite stoichiometry, the resulting phase-pure mullite is a high density, fine grain size ceramic body.
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Effect of waste polyethylene addition on the properties of white portland cement
Miguel A. Valenzuela,Francisco J. Jiménez,Lucía Téllez,이수완,Heberto Balmori-Ramirez 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.2
The effect of the addition of organic compounds (OC) an ordinary white Portland cement (WPC), on the properties such as compressive strength, fluidity, setting time, porosity and heat of hydration has been studied by adding 0.10-0.80 weight % of OC into the cement. The mixture of organic compounds obtained from a thermo-depolymerization of waste polyethylene (WP)and hydroxylation was composed by alcohols, alkenes and alkanes. The compressive strength was significantly dependent on the amount of OC. The highest value (45.3MPa) was found by adding 0.35 wt.% of the OC. The porosity of the modified WPC did not change in the range 0-0.4 wt.% OC, however from 0.5-0.8 wt.% OC caused a linear increase of the porosity.
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