微波水解法制备均分散α—Fe2O3纳米粒子的初步研究

微波水解法制备均分散α－Ｆｅ２Ｏ３纳米粒子的初步研究＊汤勇铮（皖南医学院生化组芜湖２４１００１）张文敏＊＊（安徽师范大学化学系芜湖２４１０００）关键词微波辐照水解氧化铁中图分类号Ｏ６１４．８１１均分散氧化铁胶体粒子有着广泛的应用［１］，可以用作制备催...     

不同晶化度γ-FeOOH的合成及其液相转化研究

进行了空气氧化Fe(OH)2悬浮液, EDTA作用下可见光诱导, 不同温度(14～20 ℃)制备不同晶化度γ-FeOOH的研究, 进行了其沸腾回流液相转化历程的探讨. 结果表明: 随温度的升高, γ-FeOOH的晶化程度变差; 而γ-FeOOH的晶化程度越差, 在液相沸腾回流时就越易转化成α-Fe2O3, 反之则易转化为α-FeOOH. 在pH近中性, 微量Fe(II)存在条件下低晶态的γ-FeOOH可以快速转化为均匀球形的α-Fe2O3.     

Study on the strength of cold-bonded high-phosphorus oolitic hematite-coal composite briquettes

Composite briquettes containing high-phosphorus oolitic hematite and coal were produced with a twin-roller briquette machine using sodium carboxymethyl cellulose, molasses, starch, sodium silicate, and bentonite as binders. The effect of these binders on the strength of the composite briquettes, including cold strength and high-temperature strength, was investigated by drop testing and compression testing. It was found the addition of Ca(OH)₂ and Na₂CO₃ not only improved the reduction of iron oxides and promoted dephosphorization during the reduction-separation process but also provided strength to the composite briquettes during the briquetting process; a compressive strength of 152.8 N per briquette was obtained when no binders were used. On this basis, the addition of molasses, sodium silicate, starch, and bentonite improved the cold strength of the composite briquettes, and a maximum compressive strength of 404.6 N per briquette was obtained by using starch. When subjected to a thermal treatment at 1200℃, all of the composite briquettes suffered from a sharp decrease in compressive strength during the initial reduction process. This decrease in strength was related to an increase in porosity of the composite briquettes. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed that the decrease in strength of the composite briquettes could be caused by four factors: decomposition of bonding materials, gasification of coal, transportation of byproduct gases in the composite briquettes, and thermal stress.     

Grate-kiln pelletization of Indian hematite fines and its industrial practice

Indian hematite fines normally have a high iron grade and minor impurities; they are usually used as sinter fines for feeding into a blast furnace. In this work, the grindability properties of two kinds of Indian hematite fines and the roasting behaviors and induration characteristics of pellets made from these fines were revealed through experiments involving dry ball milling and small-scale and pilot-scale tests. In addition, the microstructures of the particles of ground India hematite fines and fired pellets were investigated using optical microscopy. On the basis of the results, a grate-kiln production line with an annual output of 1.2 Mt of oxidized pellets was established in India. This pellet plant operates stably and reliably, further confirming that preparing high-quality pellets with Indian hematite fines pretreated by dry ball milling is an industrially feasible process.     

高压辊磨机粉碎贫赤铁矿产品粒度特性

研究了贫赤铁矿经高压辊磨机开路、边料循环闭路和筛分全闭路粉碎后产品的粒度特性.试验结果表明:随着辊面压力的增加,粉碎产品粒度降低,分布更加均匀,破碎比F50/P50的增长速率高于破碎比F80/P80和F20/P20的增长速率;随着边料循环量的增加,粉碎产品的粒度降低,分布更不均匀,破碎比F80/P80的增长速率高于破碎...     

宁乡式铁矿床成因的新认识

鄂西宁乡式铁矿分布广、规模大 ,普遍发育赤铁矿鲕粒。赋矿层位为加里东运动后第一个海浸沉积序列的碎屑岩向碳酸岩的过渡相 ,岩相古地理环境控制作用明显。铁矿层中赤铁矿鲕粒繁多 ,结构复杂 ,与碳酸盐鲕粒成因非常相似 ,为强烈搅动环境中的机械沉积物。经波浪和潮汐水流再次搬运富集 ,最后定位于中、弱环境或相对低凹的近滨相和远滨相上部。     

高磷赤铁矿采用 CaCl2气化脱磷的试验研究

对高磷赤铁矿在烧结过程中添加CaCl2气化脱磷进行热力学分析,并通过微型烧结试验对影响气化脱磷率的因素进行研究。结果表明,在烧结过程中添加CaCl2可以使高磷赤铁矿中的 P元素以 PCl3气体形式随烧结废气排出;气化脱磷率受配碳量、加热温度、C aC l2加入量、矿石碱度等因素影响;当配碳量为4％、加热温度为900℃、CaCl2加入量为1．36％、通过添加白灰使矿石碱度增加到1．2时,脱磷率可以达到18．3％。     

Influence of Amines on Formation and Texture of Uniform Hematite Particles

The structure and properties of hematite particles obtained by hydrolysis of ferric chloride solution doped with various kinds of amines were examined by TEM, XRD, TG-DTA, N₂and H₂O adsorption, and zeta potential measurements. The shape of precipitates was concentration dependent; they changed from large spheres (diameter: ca. 820 nm) to cubes (edge length: ca. 400 nm) via double-spheres (long axis length: ca. 600 nm) with increasing monoamine concentrations. This effect was enhanced by increasing their pK_avalues. Much pronounced effects of di- and triamines on the particle formation were observed; cubic and double-spherical particles were obtained at a much lower concentration of di- and triamines and small spherical (diameter: ca. 100 nm) and diamond-like (long axis length: ca. 100 nm) particles were further produced at higher concentration. It was suggested that the acceleration of the rate of phase transformation from β-FeOOH to hematite induced by amines plays an important role for producing fairly uniform hematite particles with different shape and size. The hematite particles produced with amines contained small amounts of OH⁻ions in the lattice but were confirmed to be nearly single crystal.     

Electrical surface charge and potential of hematite/yttrium oxide core–shell colloidal particles

Interest in the synthesis of composite colloidal particles consisting of a core and shell with different compositions stems from the fact that such particles can be useful in processes where the properties of both core (e.g., size and shape homogeneity, ease of preparation in large amounts, magnetic characteristics, etc.) and shell (interfacial properties, porosity, chemical stability, etc.) might be of interest. However, the applicability must be based on a proper characterization of those properties. In this work, colloidal spheres of hematite (α-Fe₂O₃) were used as nuclei of mixed particles where the shell is yttrium oxide. The electrical properties of the aqueous interface are compared to those of the pure oxides by means of potentiometric titration of their surface charge and potential against pH, as a function of indifferent electrolyte concentration. It is found that the mixed particles efficiently mimic yttrium oxide, since the behavior of their surface electrical characteristics closely resembles that of the latter compound. Differences are found, however, that can be ascribed to an incomplete or porous coverage, but such divergences are of little significance when an overall comparison is carried out. Received: 30 January 2001 Accepted: 11 July 2001     

纺缍形α-Fe2O3/聚苯乙烯复合高分子微球的制备、表征及等电性研究

以纺缍形α-Fe2O3超微粉为内核，过硫酸钾为引发剂，聚乙二醇为分散剂和稳定剂，乙醇／水为分散介质，苯乙烯为单体，用改进的分散聚合法合成了核／壳型纺锤形的高分子微球，并用XRD、TEM和IR进行了表征。粒子的分散性较好，粒径分布窄。由于亲水性的α-Fe2O3与亲油性的苯乙烯亲合性较差，在实验中采用了超声分散、预先溶胀和预先吸附引发剂、分散剂的方法，增强了粉末表面的亲油性，合成的高分子微球，其长轴平均为0．26μm，短轴平均为0．09μm，轴比为2．9，同时测定了不同pH值时粒子包膜前后的Zeta电位值，并根据粒子等电点的变化计算出包膜厚度，与电镜照片的结果比较吻合。