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Synthesis of Barium-Ferrite Ultrafine Particles by a Hydrothermal Method

水热法合成钡铁氧体超细颗粒

基本信息

批准号：
63550706
负责人：
KUMAZAWA Hidehiro
金额：
$ 1.34万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

Barium-ferrite ultrafine particles were synthesized from two kinds of starting materials; either ferric nitrate or goethite and barium hydroxide, by means of a hydrothermal method. The effects of alkali (NaOH) concentration, stirring speed in the autoclave, hydrothermal temperature and time on the particle shape and size were studied, and the mechanism of particle formation was deduced. The reaction conditions were clarified for which hexagonal plate-like particles of less than 0.1mum in size, suitable for coated perpendicular magnetic recording media, are synthesized.In the hydrothermal synthesis from an aqueous suspension containing ferric nitrate and barium hydroxide, the nucleation and the particle growth occur simultaneously in the early stage of the reaction. After about lh has passed, the particle growth due to Ostwald ripening becomes dominating. As the temperature and hence the pressure in the autoclave rises, the rate of particle growth increases and particles grow up to larg … More e sizes. The particle size decreases with increasing molar ratio (R) defined by (OH^-]/[NO^-_] and increasing stirring speed (n). When R <greater than or equal> 6 and n <greater than or equal> 3OOrpm at 300ﾟC, hexagonal plate-like Ba-ferrite parti- cles of less than 0.1mum in size and 0.02mum in thickness can be producedHexagonal plate-like Ba-ferrite particles of submicron size are also prepared when goethite is employed as a reactant. At 300ﾟC, Ba-ferrite was formed after a short hydrothermal treatment. As the treatment proceeded, the particle size decreased. This may be due to the fact that the crystallinity is enhanced by the treatment. The particle size decreases with rising temperature and increasing stirring speed and alkali concentration.The uncertainty of size distribution of goethite particles is apt to cause a wide size distribution of prepared Ba-ferrite particles. Therefore, the operating conditions in which extremely fine goethite particles of a narrow size distribution are produced, were searched for. By shirting the oxygen concentration in the feed stream fed to the bubble column with a draft tube to a lower level at a low conversion, the size distribution of the prepared particles becomes narrow (geometric standard deviation less than 1.18). Less

以硝酸铁和针铁矿与氢氧化钡为原料，采用水热法合成了钡铁氧体超微粒子。研究了碱浓度、釜内搅拌速度、水热温度和时间等因素对纳米粒子形貌和尺寸的影响，并对纳米粒子的形成机理进行了探讨。本文阐明了用硝酸铁和氢氧化钡水热合成法制备尺寸小于0.1 μ m的六方片状颗粒的反应条件，在反应初期，成核和颗粒生长同时发生。经过约1小时后，由于奥斯特瓦尔德熟化而导致的颗粒生长成为主导。随着温度的升高，高压釜中的压力也随之升高，颗粒生长的速度加快，颗粒长大到较大的尺寸。 ...更多信息 e尺寸。粒径随着由（OH^-]/[NO^-]定义的摩尔比（R）的增加和搅拌速度（n）的增加而减小。当R6<greater than or equal>和n3 <greater than or equal>OOrpm在300 ℃时，可得到尺寸小于0.1 μ m、厚度小于0.02 μ m的六方片状钡铁氧体克莱斯，以针铁矿为反应物时，也可得到亚微米尺寸的六方片状钡铁氧体颗粒。在300 ℃下，经过短时间的水热处理后，形成了钡铁氧体。随着处理的进行，颗粒尺寸减小。这可能是由于通过处理提高了结晶度。随着反应温度的升高、搅拌速度的增加和碱浓度的增加，颗粒尺寸减小，针铁矿颗粒尺寸分布的不确定性容易导致制备的钡铁氧体颗粒尺寸分布较宽。因此，研究了生产窄粒度分布的极细针铁矿颗粒的操作条件。通过在低转化率下用导流管将进料至泡罩塔的进料流中的氧浓度分流至较低水平，制备的颗粒的尺寸分布变窄（几何标准偏差小于1.18）。少