隐晶质石墨纯化研究进展

本文详细介绍了目前国内外隐晶质石墨提纯的各种方法,主要有浮选法、碱酸法、氢氟酸法、氯化焙烧法和高温提纯法,系统地阐述了它们的基本原理、工艺条件、研究进展,并对各种方法的优缺点进行了对比。     

隐晶质石墨在化学作用下的结构变化

本文研究了隐晶质石墨原矿,中间产品及高碳石墨,获得了不同阶段隐晶石墨的结构参数,经过化学处理取得类似鳞片石墨的层间化合物,再经高温煅烧,水洗,其结构有可逆性变化,在织构形貌上也有变化。隐晶质石墨与酸碱作用,其微晶中插入了某些基因,而杂质并未在衍射谱线上显示出来。     

隐晶质石墨提纯试验研究

以某地隐晶质石墨为原料,采用酸碱法(高温熔融法)对其进行提纯试验研究。结果表明:酸碱法(高温熔融法)可使固定碳含量为79.82%的隐晶质石墨提纯至固定碳含量为97.65%的产品。     

搅拌磨湿法制备氧化铝超细粉的研究

以粗颗粒氧化铝粉为原料,采用搅拌磨湿法工艺制备了-5．0um颗粒产率为99．68％的氧化铝超细粉。按正交表L16（4^5）安排正交试验,通过方差分析确定了制备氧化铝超细粉的最佳球磨条件,并分析了各因素对球磨过程的影响程度。在本研究的实验条件下,制备氧化铝超细粉的最佳条件为：球磨质量分数50％、球磨时间10．0h、搅拌转速500r／min、球料比7：1。     

实验室小型超细粉体搅拌球磨机研制

描述了所研制的适合于实验室使用的超细粉体搅拌球磨机,介绍了基本结构、工作原理、性能特点及其试验案例.     

实验测试方法鉴定隐晶质石墨的探讨

随着石墨应用范围的不断拓宽,鳞片石墨资源有限,区分煤与土状石墨的工作就显得尤为重要.隐晶质石墨和高变质无烟煤在地质工作中很难鉴别,现行相关的规范和工业指标也很难区分二者.在总结以往工作经验基础上,利用实验测试手段对某地区样品进行采集分析,鉴定矿物种类,避免该地区造成石墨矿资源的浪费.     

高温碱煅烧法提纯隐晶质石墨

介绍了碱煅烧法提纯石墨的研究。探讨了碱提纯法过程中包括煅烧温度、水洗条件、酸浸条件等优选。获得的理想条件是NaOH与石墨质量比为0．7：1混合,500℃煅烧,在室温下用3．6％的盐酸酸洗30min,得到的提纯样品经热分析和XRD、IR分析,证实其纯度从原样的62．43％提纯到98．60%,对提纯液中其他组分进行了回收。     

隐晶质石墨的高温碱煅烧法提纯工艺研究

以隐晶质石墨为原料,从理论上阐述了采用高温碱煅烧法提纯石墨的原理,研究了碱量,煅烧温度、煅烧时间、酸的用量、浓度、酸洗温度、酸洗时间等工艺条件对提纯效果的影响。结果表明：用高温碱煅烧法提纯隐晶质石墨,可使石墨的含碳量达到９６％以上。     

高温石墨化提纯晶质（鳞片）石墨

以晶质(鳞片)石墨为原料,采用石墨化高温提纯原理,研究不同纯度的坩埚、晶质石墨及石墨化温度等条件对提纯效果的影响。结果证明：用高温石墨化法提纯晶质石墨,可使石墨的含碳量达到99．99％以上。     

搅拌磨在加工硅酸锆超细粉中的应用

硅酸锆超细粉作为釉料乳浊剂广泛用于卫生洁具、墙地砖、釉面砖、炻器制品、工艺陈设瓷及特种陶瓷的白釉、色釉,可提高釉面光泽度、白度产使釉面柔润。起乳浊作用的主要残留在釉中未溶解的原始硅酸锆微细粒子,也就是说,获得最佳乳浊效果的首要条件是硅酸锆的颗粒细度。而目前国内硅酸锆产品加工水平仍为初级,生产技术落后,加工设备为普通球磨机,细度仅为325目,对改善陶瓷卫生洁具和高档砖釉面效果不明显,只适用于中、低档陶瓷产品。针对这种情况,我院于1997年初使用超细粉碎设备搅拌磨深加工硅酸锆超细粉,粉碎效果较佳。现根据生产实践,探讨一下搅拌磨在加工硅酸锆超细粉上的应用及产生超细 粉碎的因素。     

Parameter effects on wet ultrafine grinding of limestone through slurry rheology in a stirred media mill

Wet ultra-fine grinding of a limestone powder (< 100 μm) has been investigated in a stirred media mill with respect to the effect of slurry rheology. The grinding results obtained by various parameters (i.e., molecular weight of a dispersant, solids concentration, additive dosage, addition method and beads load) are evaluated in terms of energy efficiency and the fineness of a product. A polymeric dispersant called Dispersant S40 with a molecular weight of 5500 gives the best grinding results. For a certain level of beads load, an optimal solids concentration exists. In the case of the additive dosage of Dispersant S40 at 0.1 wt.% or more, a smaller additive amount of Dispersant S40 gives a higher energy efficiency and a smaller median size at a lower level of specific energy input. However, the excessive amount of the dispersant could cause a cushion layer formed on milling beads and thus lowers stress intensities from the collisions of milling beads, leading to an inefficient milling operation. This can be avoided by either the multi-point addition of the dispersant or a higher beads load (≥ 83 vol.%). In addition, it was found that the higher the beads load, the better the cumulative energy efficiency, and the smaller the product size at the same specific energy consumption. For a given solids concentration, the relationships between the specific surface area and the particle size of an FP product and the additive amount of Dispersant S40 are explored, respectively. Furthermore, an empirical particle size-energy model provides a good fit (R² > 0.991) to the grinding results under the experimental conditions investigated.     

Mechanical production and stabilization of submicron particles in stirred media mills

A joint research project between the Technical University of Braunschweig and the Technical University of München investigates the possibilities for the production of stable product suspensions in a particle size range smaller than 100 nm. This paper shows the experimental setup which allows the measurement of the most important electrochemical properties and the analysis of the particle size distribution of the product suspension as well as an adjustment of the pH value for stabilization during the comminution process. Results for comminution of fused corundum with different grinding media materials and grinding media sizes are shown. In addition, results showing the influence of the electrostatic stabilization on the grinding progress are presented. Further, the rheology of the product suspension is examined depending on grinding progress and suspension stability.     

一种新型沉积微晶白云母的超细粉碎研究

采用介质搅拌磨、球磨机、超音速气流磨三种不同的粉碎设备 ,在不同的工艺条件下对一种新型沉积微晶白云母进行超细粉碎。研究表明 ,粉碎结果最好的设备是超音速气流磨 ,最佳的工艺条件是工作气体压力 0 .7MPa ,给料电流 40mA ,适当添加助磨剂时 ,D90 达 1.18μm。     

Catalytic properties of ultrafine molybdenum-cerium oxide particles prepared by the sol-gel method

The structure and catalytic properties of ultrafine Mo-Ce oxide particles prepared by the sol-gel method have been studied by using X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, laser Raman spectroscopy and microreactor tests. It has been shown that for selective oxidation of toluene to benzaldehyde the ultrafine Mo-Ce oxide particles exhibit higher catalytic activity than the larger oxide particles prepared by a conventional coprecipitation method. The unique catalytic properties of ultrafine Mo-Ce oxide particles may be correlated not only to the interaction between molybdenum oxide and cerium oxide, but also to the higher reactivity of lattice oxygen species in the ultrafine oxide matrix. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optimization of some parameters of stirred mill for ultra-fine grinding of refractory Au/Ag ores

In this study, optimization of some parameters of stirred mill on ultra-fine grinding of refractory Au/Ag ores was performed. A three-level Box-Behnken design combining a response surface methodology (RSM) with quadratic programming (QP) was employed for modelling and optimization of some operating parameters in ultra-fine grinding. Grinding tests were carried out in a laboratory scale pin-type vertical stirred mill. The relationship between the response, i.e. d₈₀ size, and four grinding parameters, i.e. ball diameter, grinding time, ball charge ratio and stirrer revolution was presented as empirical model equations. Analysis of variance showed a high coefficient of determination value (R² = 0.9698), thus ensuring a satisfactory of the second-order regression model with the experimental data.The model equations were then optimized using the quadratic programming method to minimize for d₈₀ size within the experimental range studied. The optimum conditions were found to be 1.61 mm for ball diameter, 11.50 min for grinding time, 80% for ball charge ratio and 745 rpm for stirrer revolution for this grinding process.In order to verify the improvement of grinding performance using the optimal level of control factors three verification experiments were conducted, and the results for d₈₀ was 3.37 μm, which were smaller than those obtained in the initial tests.     

A comparison of the results obtained from grinding in a stirred media mill lignite coal samples treated with microwave and untreated samples

Various studies have been carried out on the effect of microwave-treatment on grinding different types of coal. However, the effect of microwave treatment on grinding coal samples −3.35 mm in size which can be considered to be fine is still under investigation. The purpose of this paper is to make contributions to these studies conducted. In the study, lignite coal samples with pyritic sulphur and 25% structural moisture were crushed below −3.35 mm particle size using jaw and cone crushers and then classified into three different mono size groups by Russel sieve. For a complete removal of the structural moisture from the lignite coal, a microwave application with 600 W needs approximately 35% more energy consumption than that with 850 W. The untreated coal samples and the ones treated with microwave at 850 W were ground for 5, 15, 30, 60, 120 s in a stirred media mill. The breakage rates of microwave-treated coal increased and accordingly the ground products of microwave-treated coal yielded finer particles than −106 μm as compared to untreated coals. The untreated and microwave-treated feed coals of −3350 μm and −1180 μm particle sizes were ground for 2 min in the stirred media mill. It was found that the increases in the rate of weight percentages for −106 μm particle size fraction after 2 min of grinding of untreated and microwave-treated feed coals of −3350 μm and −1180 μm were found to be 15.81% and 2.69%, respectively. Moreover, Hardgrove Index (HGI) test results of lignite coal showed that the HGI index value increased by approximately 23% after microwave treatment with 850 W.     

氢氧化铝的湿式超细粉碎试验研究

采用介质搅拌磨进行了氢氧化铝的湿式超细粉碎试验,研究了助磨剂品种及用量、矿浆质量分数、介质／物料比、转子转速、研磨时问等对氢氧化铝超细粉碎效果的影响。结果表明,在适宜的工艺条件下,超细粉碎后氢氧化铝的粒度可以达到d50=0．75um,d97=1．58um。     

Preparation of aluminum ultrafine particles by anodizing aluminum foil in acidic electrolyte containing chloride ions

Anodization of aluminum in acidic electrolyte containing chloride ions was used to prepare aluminum ultrafine particles (Al UFPs) for the first time. In addition, the influence of different acid electrolyte was investigated and the mechanism of generating Al UFPs is analyzed. It is found that the pitting corrosion of chloride ions plays an important role in preparing Al UFPs and the acidification of the electrolyte is in favor of the preparation. Al UFPs with different shape and size distribution were obtained via changing the type of acid. Finally, the model of generating Al UFPs via this method is proposed.     

Contact angle and vacuum floatability of ultrafine size particles

The contact angle of ultrafine size particles has been evaluated using 1 µm monosize SiO₂ particles of various degrees of wettability. The contact angle was determined by film flotation and Zisman plots. Chlorotrimethylsilane (CTS) was used to methylate the SiO₂ particle surface and establish the level of surface wettability. Also, the vacuum floatability of the methylated ultrafine SiO₂ particles was assessed to correlate it to the contact angle. This vacuum floatability was very low below 40º and increased monotonically above this contact angle value because of favorable bubble nucleation and a greater stability of the bubbles on the hydrophobic surface. Free energy of bubble nucleation on the hydrophobic surfaces has been estimated and correlated to the vacuum floatability of the ultrafine particles.