• 제목/요약/키워드: bayerite

검색결과 26건 처리시간 0.016초

나노 및 마이크로 알루미늄의 가수분해에 의한 알루미늄 수산화물의 형성 (Formation of Aluminum Hydroxides by Hydrolysis of Nano and Micro Al Powders)

  • 오영화;이근희;박중학;이창규;김흥회;김도향
    • 한국분말재료학회지
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    • 제12권3호
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    • pp.186-191
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    • 2005
  • A formation of aluminum hydroxide by hydrolysis of nano and micro aluminum powder has been studied. The nano aluminum powder of 80 to 100 nm in diameter was fabricated by a pulsed wire evaporation (PWE) method. The micro powder was commercial product with more than $10\;{\mu}m$ in diameter. The hydroxide type and morphology depending on size of the aluminum powder were examined by several analyses such as XRD, TEM, and BET. The hydrolysis procedure of micro aluminum powder was different from that of nano aluminum powder. The nano aluminum powder after immersing in the water was transformed rapidly to a nano fibrous boehmite, accompanying with a remarkable temperature increase, and then further transformed slowly to a stable bayerite. However, the micro powder was changed to the stable bayerite slowly and directly. The formation of fibrous aluminum hydroxide from nano aluminum powder might be due to the fine cracks which were formed by hydrogen gas pressure on the surface hydroxide layer during hydrolysis. The nano powder with large specific surface area and small size reacted more actively and faster than the micro powder, and transformed to meta-stable hydroxide in relatively short reaction time. Therefore, the formation of fibrous boehmite is special characteristic of hydrolysis of nano aluminum powder.

AlCl3 폐액으로부터 다공성 Boehmite Gel의 제조 (Preparation of Porous Boehmite Gel from Waste AlCl3 Solution)

  • 박병기;이학수;김영호;이정민
    • 한국세라믹학회지
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    • 제41권11호
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    • pp.864-871
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    • 2004
  • 폐 염화알루미늄(AlCl$_3$) 수용액과 수산화나트륨(NaOH) 용액의 가수분해 반응에 의해 무정형의 수산화알루미늄 겔을 석출시키고, 이를 숙성하여 다공성 유사베마이트(pseudo-boehmite) 겔을 제조하였다 pH를 7.6~11.6 범위로 조절하고 반응온도를 60~10$0^{\circ}C$로 변화시켜 2~24시간 숙성시켰을 때, 겔 침전물의 결정변화, 적외선흡수스펙트럼의 변화, 비표면적 및 기공구조의 변화를 조사하여 최대 기공부피를 갖는 유사베마이트 겔의 제조조건을 확립하였다. pH 7.6~9.6 범위에서 석출된 겔 침전물로부터 250~357 $m^2$/g 정도의 비표면적과 0.4~0.74 cc/g의 기공부피 그리고 58~l14$\AA$의 평균기공크기를 갖는 다공성 유사베마이트가 제조되었으며, pH 10.6~11.6 범위에서 석출된 겔 침전물로부터는 기공이 거의 없는 베이어라이트(bayerite)가 제조되었다.

부분 가수분해된 AlN 분말로부터 산질화 알루미늄(AlON)의 합성 및 소결 (Synthesis of AlON from Partially Hydrolyzed AlN Powder and its Sintering)

  • 김두영;최상욱;남건태
    • 한국세라믹학회지
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    • 제31권11호
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    • pp.1362-1368
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    • 1994
  • The hydrolysis of aluminum nitride was increased gradually with increasing reaction time from 1 hrs to 24 hrs and/or with decreasing the addition of the reaction water from 100 mι 100mι. Amorphous aluminum hydrate, formed in the beginning of the reaction, was transformed to bayerite and to pseudoboehmite at below and above 8$0^{\circ}C$, respectively. Aluminum oxynitride was synthesized by heating the partially hydrolyzed aluminum nitride at 1$700^{\circ}C$ for 4 hrs or at 175$0^{\circ}C$ for 30 min. AlON specimen with 1 wt% of Y2O3 that was molded and then sintered pressurelessly at 190$0^{\circ}C$, exhibits 98% of the theoretical density and a translucency of 68% in the visible ray zone.

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알루미나수화물(水和物)의 침전(沈澱)pH가 물성(物性)에 미치는 영향(影響) (Effect of pH of Precipitation on Physical and Chemical Properties of Hydrous Aluninum Oxide)

  • 이계주
    • Journal of Pharmaceutical Investigation
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    • 제6권2호
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    • pp.95-100
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    • 1976
  • A study on the effect of the pH of precipitation on the acid consuming capacity, aging stability, physical and chemical properties of hydrous aluminum oxide prepared by the reaction of aluminum chloride and ammonium hydroxide solution was carried out by means of X-ray diffraction, IR spectra and differential thermal analysis. The results from these experiments are as follows: 1. Hydrous aluminum oxide precipitated at lower pH showed better acid consuming capacity, higher stability and more anion contained in the structure than that prepared at higher pH. 2. The hydrous aluminum oxide prepared at lower pH is amorphous and that prepared at higher pH is crystalline hydrated hydrous aluminum oxide, i.e., Bayerite and these results are conformed to Rhee's hypothesis. 3. The rate of loss of reactivity and the end-point reactivity are related to the pH of precipitation.

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Formation of an aluminum hydroxide nanofiber by a hydrolysis of aluminum nanopowder

  • Oh Young-Hwa;Lee Geun-Hee;Park Joong-Hark;Rhee Chang-Kyu;Kim Whung-Whoe
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2004년도 International Symposium on Powder Materials and Processing
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    • pp.80-81
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    • 2004
  • The results obtained are summarized as follows; (1) Boehmite produced in the high temperature and acid region showed a nano fibrous shape with several nm in diameter and several hundreds nm in length having high specific surface areas with a maximum value of $409m^2/g$. (2) In order to obtain nano fibrous boehmite with high surface areas from nano metal powder, the hydrolysis reaction should be done at a high temperature over $50^{\circ}C$, high acidity under pH 6, and terminated before a transition to the bayerite phase.

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침전법으로 제조한 Alumina 분말의 특성(1): 알루미늄 수산\ulcorner루 (Properties of Alumina Powder Prepared by Precipitation Method(I): Aluminum Hydrate)

  • 홍기곤;이홍림
    • 한국세라믹학회지
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    • 제25권2호
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    • pp.111-116
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    • 1988
  • Aluminum hydrates were prepared by precipitation method using Al2(SO4)3$.$18H2O as a starting material and NH4OH as precipitation agent. The phases of aluminum hydrate were changed from amorphous aluminum hydrate to pseudo-boehmite of AlOOH form and bayerite, gibbsite, hydragillite and norstrandite of Al(OH)3 form with increasing pH. As pH increased, agglomeration phenomena were reduced. Aluminum hydrates of AlOOH and Al(OH)3 form represented dehydration of structural water near 175$^{\circ}C$ and 385$^{\circ}C$, and 280$^{\circ}C$, respectively. As the ratio of Al(OH)3 to AlOOH increased, specific surface area was reduced.

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Effect of Humidity on Physico-chemical Properties of Hydrous Aluminum Oxide

  • Rhee, Gye-Ju;Han, Kwan-Sub
    • 약학회지
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    • 제21권2호
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    • pp.101-109
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    • 1977
  • The effect of humidity on the aging process of hydrous aluminum oxide prepared by the reaction of aluminum chloride and sodium bicarbonate solution at pH 7.8, which was then kept in various atmosphere under relative humidity at 37.deg. was observed by the measurements of acid consuming capacity, X-ray diffraction and IR absorption. The humidity was one of the important factors influencing the aging process of hydrous aluminum oxide during storage. The higer the humidity, the more was accelerated age, crystalize and loss in acid reactivity. Depending on the humidity, the aging product was different, especially, in the case of up to the relative humidity of 72%, it forming bayerite. On the other hand, the hydrous aluminum oxide aged below the relative humidity of 50% was still amorphous even after 120 days storage. When hydrous aluminum oxide was aged under higher humidity, definite IR absorption bands develop as the hydroxys become part of an ordered structure, and it showed their characteristic absorption band around 1630 and 1060 cm$^{-1}$.

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

  • 박병기;서정권;이정민;서동수
    • 한국세라믹학회지
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    • 제35권10호
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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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Bauxite로부터 습식 산처리법에 의한 알루미나 분체의 제조 및 그 이용에 관한 연구(I) : Bauxite로부터 Aluminum Hydrate Gel의 제조 (A Study on the Preparation of Alumina Powders from Bauxite by Wet Acid Process and Their Utilization(I) : Preparation of Aluminum Hydrate Gels from Bauxite)

  • 박민준;조철구;배원태
    • 한국세라믹학회지
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    • 제27권6호
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    • pp.747-754
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    • 1990
  • Aluminum hydrate gels were prepared from the mixtures of bauxite and ammonium sulfate by wet acid process. Optimum conditions for obtaining the maximum yield( 99%) of aluminum hydrates from the same amount of bauxite were confirmed as follows ; 1. Mixing ratio ; addition of 25mole% of ammonium sulfate to 1mole of bauxite. 2. Calcination ; heated at 350℃ for 1hr. 3. Extraction ; leached at 95℃ in 1% H2SO4 for 90min. 4. pH of precipitating solution; slight below 7.0. Amorphous aluminum hydrates were precipitated at the pH lower than 8.5, but the precipitates crystallized to bayerite at the pH was 10. Mean diameter of α-Al2O3 powders which were obtained by calcining the aluminum hydrates was below 0.2㎛, and EDS analysis revealed than SiO2 was it's primary impurity.

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합성 Dawsonite의 물리적, 화학적 성질 (Some Physical and Chemical Properties of Synthesized Dawsonite)

  • 권상욱
    • 대한화학회지
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    • 제13권2호
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    • pp.149-156
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    • 1969
  • $NaAl(OH)_2CO_3$was synthesized using colloidal earth (Allophane) as the starting material and some of its were studied in detail. It was found that Dawsonite was formed in the pH range (pH 12.5~12.0) that the concentration of $HCO_3^-$ was just begun to increase and the presence of $HCO_3^-$ in the product was clarified from the infrared absorption spectrum. The chemical formular of Dawsonite was therefore presumed as $NaAlO (OH) HCO_3$. From toahhe results of X-ray powder diffraction, both peaks at 5.7 $\AA$ and 2.8 $\AA$ were observed, and fibrous crystalline structure was observed from electron micrograph and also found from the microscopic electron diffraction at 5.7 $\AA.$ Therefore the fibrous axis was considered as =Al=O2=Al=O2=Al=(*image) direction. True specific gravity of Dawsonite was 2.44 and its porosity was 91.4%. It was practically insoluble in water, but decomposed in the boiling water to form Pseudo Boehmite. Stable pH range of Dawsonite was about 4.5~11.5. From the results of D.T.A. and T.G.A., it was observed that $CO_2$was liberated at $350^{\circ}C$, and $H_2O$ at $650^{\circ}C$, and converted into strongly hygroscopic $NaAlO_2$, which was easily decomposed in water into $\beta-Al(OH)_3(Bayerite)$ and NaOH.

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