硅灰石针状粉制备技术的现状与设想

具有足够长径比的超细硅灰石针状粉在工业上有着极高的应用价值,提高硅灰石产品的长径北,关键在于在粉碎过程中保持矿物原有的结晶结构.硅灰石针状粉超细粉碎技术的关键是如何使加工过程更趋符合其粉碎机理的要求,但目前还有一定的差距.本文的目的就在于总结现有的硅灰石超细粉碎技术,找出存在的问题,提出设想,以便促进该技术的更大发展.     

针状硅灰石在大规格薄型瓷质砖中的应用

主要介绍了天然针状硅灰石在国内的地理分布情况以及相关性能特征。并对针状硅灰石在大规格薄型瓷质砖生产过程中的应用进行了分析。重点研究了相关制品的工艺流程、工艺参数等,最后给出了生产过程中的具体建议。     

硅灰石粉体表面改性红外光谱分析与机理研究

硅灰石是中国优势非金属矿产资源之一,本研究是在大量实验室试验和半工业试验研究基础上,应用多学科的相关理论及现代测试分析技术对硅灰石超细粉碎-表面改性一体化工艺进行试验研究,通过红外吸收光谱分析和X-射线衍射粉晶分析,证明了表面改性产品结合物的存在并探索了制备机理.     

针状硅灰石/尼龙6复合材料的制备和性能研究

将针状硅灰石和尼龙6经双螺杆挤出机熔融共混,制备了硅灰石/尼龙6复合材料。研究了硅烷偶联剂种类、偶联剂质量分数、共混工艺条件和硅灰石质量分数对复合材料性能的影响。用光学显微镜和扫描电子显微镜分别观察了硅灰石共混前后的形貌和硅灰石/尼龙6复合材料冲击试样断面的形貌。结果表明:用KH-550预处理的硅灰石比KH-560预处理的硅灰石制备的硅灰石/尼龙6复合材料的力学性能好。硅灰石采用侧喂料和较低的螺杆转速制备硅灰石/尼龙6复合材料,可以提高硅灰石/尼龙6复合材料的力学性能。随着硅灰石质量分数的增加,复合材料的力学性能提高。     

超细针状硅灰石在聚乙烯白色母粒中的应用研究

首先采用扫描电子显微镜和激光粒度仪分析了超细针状硅灰石的粒子形貌和粒径分布,并用其作为着色剂部分替代钛白粉后制备聚乙烯白色母粒,然后采用积分球式测色仪和万能力学试验机系统分析了硅灰石的细度和替代量对白色母粒试样的色彩性能的影响.结果表明:硅灰石的粒子保持了较好的长径比、粒径细、粒径分布窄;采用GY-4000超细硅灰石部...     

低模数水玻璃制备硅灰石试验研究

本文以贵州某中试厂生产的模数为1.02的水玻璃为原料,与消石灰水热法合成硅灰石.研究考察了反应时间、反应温度、搅拌速率对硅灰石制备的影响规律,在单因素实验的基础上通过正交试验,对合成工艺参数进行了优化,同时考察了回收碱浓度对制备硅灰石的影响.用X射线衍射(X-ray diffraction,XRD)、扫描电镜(Scanning electron microscope,SEM)、粒度分析仪(Grain size analyzer)、白度仪(Whiteness meter)等手段对硅灰石的物相和微观形貌进行表征.试验结果表明:低模数水玻璃制备硅灰石最佳工艺条件为:反应温度为80℃、反应时间2.5h、搅拌速率为300 rpm,SiO2反应率可达99.31％,钙硅摩尔比为1.03,硅灰石产品可达到行业二级品要求.模拟实验最大回收碱浓度为237 g/L,该方法为煤矸石资源化综合利用提供了一种新途径.     

尼龙66/针状硅灰石复合材料的制备和性能研究

以针状硅灰石为填料,用双螺杆挤出机共混制备尼龙(PA)66/硅灰石复合材料,研究了硅灰石含量、处理方法和加工工艺对复合材料性能的影响,并观察了硅灰石共混前后和PA66/硅灰石复合材料冲击试样断面的形貌。结果表明,硅灰石用KH–560预处理时比用KH–550预处理所制备的PA66/硅灰石复合材料的力学性能好。硅灰石以侧喂料方式加入并采用较低的螺杆转速时,可使复合材料具有较高的力学性能。随着硅灰石含量的增加,复合材料的拉伸强度、弯曲强度和缺口冲击强度都大幅提高。经过1%KH560预处理的硅灰石质量分数在30%时,PA66/硅灰石复合材料的力学性能最好。     

超细针状硅灰石短纤维在尼龙66中的应用

探讨了超细针状硅灰石短纤维在尼龙66(PA66)中的应用,研究了在双螺杆挤出机的混炼工艺条件下,不同配比的超细针状硅灰石短纤维对PA66物理力学性能的影响。实验表明,超细针状硅灰石短纤维的加入不仅使PA66的各种性能得到改善,而且原料成本有所下降。     

硅灰石形貌对聚丙烯结晶行为的影响

采用熔融共混法制备了聚丙烯（PP）／硅灰石复合材料,并对其结晶行为进行研究。用X-射线衍射（XRD）研究了硅灰石的加入及类型对PP的晶体尺寸及类型的影响。结果显示,硅灰石的加入不改变PP的晶型,仍为α晶,而晶粒尺寸变小,表明硅灰石有异相成核作用。相比较而言,针状硅灰石比颗粒状硅灰石的异相成核作用更明显。采用差示扫描量热仪（DSC）在各种不同冷却速率下对复合材料的非等温结晶动力学过程进行研究,并用Jeziorny法来描述这些样品的非等温结晶过程。在相同的冷却速率下,半结晶时间（t′1/2）、结晶速率常数（Zc）等数据表明复合材料的结晶速率比纯PP的快,说明硅灰石具有异相成核作用,与颗粒硅灰石相比,针状硅灰石异相成核作用更明显。     

针状硅灰石对阻燃HIPS材料性能和形态的影响

通过在阻燃高抗冲聚苯乙烯(HIPS)材料中加入不同用量的针状硅灰石的试验研究,发现一定用量的硅灰石可提高阻燃HIPS材料的断裂伸长率、弯曲弹性模量、耐热性和加工性能,而对阻燃HIPS材料的拉伸强度、冲击韧性和阻燃性能基本上无影响。扫描电子显微镜观察显示,硅灰石以一定长度的针状细条嵌入HIPS基体中,起到部分玻璃纤维的改性作用,阻燃HIPS材料的冲击断面仍为韧性断裂。     

Modeling of continuous self‐classifying spiral jet mills part 1: Model structure and validation using mill experiments

The objective of this work is to develop a milling model for a continuous self‐classifying spiral air jet mill. Its foundation is a population balance model with selection and breakage distribution functions that have been related to a minimal number of mill‐dependent and powder‐dependent parameters. Initially, experimentation is required to determine the mill‐dependent parameters for a specific mill, by milling a “base” powder at multiple operating conditions. Powder‐dependent parameters can be determined from either mill experiments or from material characterization measurements that require small amounts of powder (presented in Part 2). Ultimately, the milling model presented successfully predicts the product particle size using as inputs the feed particle‐size distribution and mill operating conditions. Three crystalline powders, sodium bicarbonate, lactose monohydrate, and sucrose, have been used to test the proposed milling model. © 2014 American Institute of Chemical Engineers AIChE J 60: 4086–4095, 2014     

Characterization of media mills based on mechanical energy applied to particles

This paper deals with the evaluation of characteristics of media mills having a different milling mechanism based on the mechanical energy applied to the particles to be processed during a milling treatment. Spherical copper powder was used as a stress-sensitive material and the milling treatment of the copper powder was carried out under various operating conditions using three types of media mills, a horizontal tumbling ball mill, vertical agitating ball mill and bead mill. The size distributions of copper powder before and after the milling treatment were measured and the deformation of copper particles was determined experimentally. The net energy applied to the copper powder was estimated from the plastic deformation of copper particles. It has been clarified that the applied energy depends strongly on the motion of media in the mill. By introducing two dimensionless parameters, which express the energy transfer efficiency from the kinetic energy of media to the particles and the motion of media in the mill, respectively, the media mills could be characterized on a uniform scale based on the applied energy regardless of milling mechanism.     

立磨用于水泥粉磨的半工业化实验探索

将实验立磨用于水泥粉磨的半工业化实验探索,通过调整实验立磨的操作参数（磨机风量、选粉机转速、主电机转速、粉磨压力等）,寻求实验立磨粉磨水泥的最佳工况;通过对产品的粒度分析,寻找产品细度细、比表面积小的原因;根据寻找出的原因提出了对实验立磨的改进。     

Roll compaction of maize powder

This paper presents a study of a roll compaction process as a dry granulation method for typical food materials such as maize powder. This process is widely applied in industry as it can continuously produce large quantities of granular product at comparatively low cost. The objectives of this work were to predict the roll compaction performance from a simple measurement involving uniaxial die compaction using the classical Johanson model. This involved determination of the optimum operating conditions for the production of granules as evaluated by apparent density.In the current work, a smooth counter-rotating rolling mill with a roller diameter of 0.08 m and a roller width of 0.20 m was used. The operating conditions for the rolling mill are shown to be influenced by parameters such as the roll gap, the roll speed, the feed powder amount, and the friction ratio. Material properties such as the compressibility factor and the angle of wall friction were investigated using uniaxial die compaction. The angle of wall friction was analysed using both contact mechanical and continuum mechanical approaches.The results indicated that this simplified approach can be used to provide a quantitative prediction of the extent of the roll compaction performance, and can be used to design optimal roller geometries and operating conditions.     

Influence of process parameters on SAC305 lead-free solder powder produced by centrifugal atomization

In the present work, a centrifugal atomizer was constructed in order to study the effects of operating parameters: rotating speed, melt feed rate, shape and size of atomizer, and oxygen content in the atomizer chamber, on the characters of SAC305 powder. It was evidenced from the experimental results that the median size of the atomized powders became smaller with increasing rotating speed, decreasing melt feed rate, and the use of larger atomizer. At same operating conditions, a cup shaped atomizer was able to give approx. 11% finer powder compared to that from a flat-disk shaped one. Median particle size appeared to be smaller with decreasing oxygen content in the chamber. SEM micrographs revealed that SAC305 particles atomized under atmospheric condition were found to form various shapes: ligament, teardrop, flake, and irregular. The shape of powder particles tends to be rounder with decreasing oxygen content in the chamber. Fine particles of SAC305 powder (− 45 μm) containing oxygen less than 100 ppm could be synthesized by purging nitrogen gas into the atomizing chamber. Production yield of the SAC305 powder increased with increasing atomizer's rotating speed, lower melt feed rate, and larger atomizer.     

Binder jetting additive manufacturing of silicon carbide ceramics: Development of bimodal powder feedstocks by modeling and experimental methods

A limitation of binder jetting additive manufacturing is the low density of fabricated parts. Mixing powders with different sizes is a promising approach to increase powder bed packing density and, hence, printed part density. However, in previous studies mixed powder feedstock was prepared by trial and error method. In this research, both modeling and experimental methods were used to prepare the bimodal powder feedstocks. Analytical packing model was introduced for irregular powders. A bimodal powder was prepared by mixing two different-sized silicon carbide powders (i.e. coarse and fine) using ball mill, and their tap densities were measured. Silicon carbide plates were printed using the coarse and bimodal powders by a commercial binder jetting system. Results showed that the modeling method could predict the tap density of bimodal powders with high accuracy. The printed parts from bimodal powder achieved higher green densities than those from the unimodal powder.     

磨煤机拉杆密封漏煤粉原因分析及解决

对我公司MP2519磨煤机拉杆密封装置结构进行了认真分析,找出了拉杆密封装置漏煤粉的原因,对原密封装置进行了改造,有效地消除该密封装置漏风、漏粉现象,延长磨煤机的检修周期,显著地改善磨煤机的运行工况。     

Flow of particulate solids through tumbling mills

The transport behavior of particulate solids flowing through tumbling mills depends strongly on the mill operating conditions. This paper presents the results of a detailed study to delineate the effect of the important operating variables on the hold-up, mean residence time and residence time distribution of particulate solids flowing through ball mills and rod mills. The effects of feed rate, media load, and mill speed on these transport parameters are discussed, emphasizing the fundamental differences between particulate transport in ball mills and rod mills. Under identical dimensionless operating conditions over the range of the investigation, the material hold-up and the Peclet number of the flow regime in the rod mill were always higher than those in the ball mill. Mechanistic interpretations of the observed transport phenomena are presented, and their implications in the context of tumbling mill analysis and design pointed out.     

球磨法制备超细镍粉及其表征

为了获得在自然条件下稳定存在的超细镍粉,通过控制行星式高能球磨机的转速、研磨时间、磨球数、运转时间、暂停间隔、转动方向等参数对镍粉进行了研磨实验,并对不同参数下的研磨结果进行了测试表征。结果表明,在转速260 r/min、研磨时间19 h、运行时间3 min、暂停时间30 s、磨球数为10个、原料5 g且晴朗天气下实验,可以制备出亚微米级超细镍粉,并在空气中稳定存在。     

Optimization of variables in grinding brass particles for paint and pigment industry

Flaky metal powders commonly used as paint and pigments, are generally produced by grinding in ball mills or vibration mills. The key to good quality powder production is to optimize the processing parameters. In the present work grinding of brass particles is studied in detail in a laboratory size ball mill to determine the optimal levels of the ball to material ratio, type and amount of additives, mill speed, ball load, etc. The quality of the powder is assessed on the basis of water coverage, degree of flattening and luster by visual inspection. Preliminary results in a 35 cm diameter ball mill with 30% ball load show that a material to ball ratio of 0.067 with a 0.1% dosage of stearic acid is required for good quality powder. For determining optimal mill speed and ball size a 2² factorial design of experiment has been followed. It has been determined that to achieve best powder quality the mill must run at 70% critical speed and the ball size must not exceed 20 mm. The quality of the powder assessed through SEM study for surface morphology and particle size analysis compares very well with the industrial samples.