气流磨粉磨超细矿渣粉的粉体性能和微观形貌研究

煤炭、粉煤灰及矿渣是用于水泥生产的原料或混凝土的掺合料,而细度是影响粉体材料性能的因素之一。本文以矿渣为材料,利用JFC-5对撞式流态化床气流磨制备了超细矿渣粉,对超细矿渣粉的粉体性能和微观形貌进行了研究。研究表明,气流磨粉磨超细矿渣粉存在粉磨平衡,超细矿渣粉颗粒分布集中,分选机转速过大,得到的矿渣粉体出现团聚现象。     

梯级粉磨铁尾矿制备超高性能混凝土的研究

展开了梯级粉磨工艺粉磨铁尾矿、石膏、矿渣及水泥熟料生产铁尾矿-矿渣基高性能胶凝材料(简称TSBC)及其性能的研究,探讨了不同粉磨工艺的粉体粒径特征及胶凝性能,对比了TSBC材料与PO52.5水泥的制备超高性能混凝土强度及耐久性差异。研究结果表明,三级粉磨较二级粉磨能更好发挥颗粒的"微磨球"效应,所得粉体材料粒径更小;粉磨中应将铁尾矿砂作为第一级粉磨材料,第一级粉磨时间不宜过长,否则导致粉体过细大量覆盖粗颗粒材料表面,降低后期粉磨效率;TSBC制备的UHPC不仅具有常规UHPC的强度甚至有更优良的耐久性能。     

有机物助磨剂对矿渣粉磨的影响

为了研究有机物碳链长度、基团数目和种类、分子量大小对矿渣粉磨的影响,采用醇类、醇胺类、磺酸盐类有机物作助磨剂,通过测量矿渣粉体比表面积、筛余、休止角,研究有机物中不同基团对矿渣粉磨的影响。结果表明:如果碳链长度相似,所含活性基团越多,粉磨效果越好;活性基团数目相同,碳链越长,粉磨效果越差;分子量大的粉磨效果不好。其中对粉磨矿渣效果来说,丙三醇三乙醇胺磺酸盐类。     

球磨与搅拌磨粉磨矿渣粉的微观形貌特性

采用小型球磨和搅拌磨对矿渣粉进行粉磨实验,运用扫描电镜样品制备技术,对球磨和搅拌磨不同粉磨阶段的矿渣粉进行微观形貌特征研究,分析不同粉磨方式粉磨过程中矿渣粉颗粒的微观形貌变化规律。结果表明,随着粉磨时间的延长,矿渣粉颗粒群的形状指数、扁平度、棱角度和表面粗糙度均减小,圆度系数增大;球磨和搅拌磨粉磨矿渣粉颗粒的微观形貌存在较大差异,粉磨时间相同时,搅拌磨粉磨矿渣粉颗粒的微观形貌优于球磨粉磨的。     

不同粉磨方式矿渣粉对矿渣水泥流变性的影响

用激光粒度分析仪（LPS）研究了球磨和立磨粉磨的矿渣粉的粒度分布，用旋转粘度计对矿渣水泥的流变性能进行了测量。发现：球磨机所加工的矿渣粉比立磨加工的矿粉颗粒尺寸分布宽、细颗粒含量高；矿渣粉比表面积相近时，矿渣掺量在小于30%和大于40%时由球磨矿渣粉制成的矿渣水泥比立磨矿渣水泥的屈服应力和粘度小，而掺量在30%～40%之间时球磨矿渣水泥的粘度和屈服应力较立磨的稍大。此外，对矿渣粉颗粒群与水泥流变性之间进行了灰色关联分析，发现小于10μm的矿渣颗粒增加了水泥浆的屈服应力和粘度，而大于10μm矿渣颗粒却削弱了水泥浆的屈服应力和粘度。     

低活性酸性矿渣粉细度对胶结充填体早期强度的影响

为了解决以活性较低的酸性矿渣粉开发的胶凝材料胶结充填体早期强度较低的问题,利用对矿渣粉粉磨不同时间的机械活化来研究矿渣粉细度对早期强度的影响。结果表明:对原状矿渣粉粉磨1、1.5 h后,相对于原状矿渣粉的比表面积404.7m~2/kg,矿渣粉比表面积分别增大为521、577.2 m~2/kg;粉磨1 h矿渣粉的3 d抗压强度提高了33.3%,7 d抗压强度无明显增长;粉磨1.5 h矿渣粉的3、7 d抗压强度分别提高了22.2%、18.1%;矿渣粉胶凝材料的水化产物主要以针状钙矾石和团絮状C-S-H凝胶物为主,与骨料紧密粘结构成整体。     

粉磨工艺对赤泥胶结充填料性能的影响

为提高胶结充填材料的强度性能,试验研究了分别粉磨和梯级粉磨工艺对赤泥全尾砂胶结充填材料强度性能、粉体粒径以及水化过程的影响.结果表明：梯级粉磨工艺下试块的1、3、28 d最大抗压强比分别粉磨工艺下试块1、3、28 d最大抗压强度分别高出21%、16.6%、3.7%;梯级粉磨工艺使物料粉体的比表面积均高于分别粉磨工艺的粉...     

高钛矿渣的粉磨特性研究

由于攀钢高炉渣中含有20%以上的TiO2,使其利用受到很大限制,为使高钛矿渣作为掺合材料应用于混凝土,需首先了解高钛矿渣的粉磨特性。本文中研究了粉磨时间与高钛矿渣细度之间的关系,对比了高钛矿渣与普通矿渣易磨性并分析了助磨剂对高钛矿渣粉磨的影响。结果表明,高钛矿渣的易磨性较普通矿渣差,可使用助磨剂提高高钛矿渣的粉磨效率。     

黄磷矿渣的粉磨动力学研究

采用φ500mm×500mm试验球磨机对黄磷渣进行不同时间的粉磨加工,运用线性回归分析、Rosin-Rammlar-Bennet(RRB)粒度分布分析和粉磨动力学的特征粒径分析的方法,对黄磷渣进行了粉磨动力学研究和粉磨性能评价。结果表明:磨后黄磷渣粉体的比表面积、特征粒径和均匀系数与粉磨时间的对数或双对数呈线性关系,且黄磷渣的加工细度不宜高于350 m2/kg。     

KHM170型卧辊磨制备钢渣超细粉工业试验研究

基于KHM170型卧辊磨的钢渣超细粉制备终粉磨工业试验系统,在给定钢渣粉、矿渣粉、水泥熟料粉的质量和粒度范围内,进行用钢渣粉部分代替矿渣粉制作水泥混凝土的强度试验。结果表明,KHM卧辊磨终粉磨系统可以实现钢渣超细粉终粉磨,可用于以热焖渣、滚筒渣为原料制备钢渣微粉的工业化生产;矿渣粉中掺加质量分数不超过30%的钢渣粉,且在满足钢渣粉比表面积大于矿渣粉比表面积和水泥熟料粉比表面积时,可以作为优选的混合材料大量用于混凝土。     

粉体堆积密度的理论计算

考察了紧密堆积时多级理想球形颗粒混合粉体的堆积密度的理论值与粒级组分数的关系,紧密堆积时颗粒的粒度分布特征,以及堆积密度的理论值与单一粒径粉体空隙体积分数、颗粒干扰宽度的相关关系。研究表明,原始堆积密度越大,多粒级理想球形颗粒混合粉体达到相同的堆积密度所需的粒级数越少,各粒级的体积含量随着粒级的增加呈指数下降,且原始堆积密度越大,下降速度越快;其粒度分布符合对数正态分布;堆积密度的理论值与单一粉体空隙体积分数、颗粒干扰宽度的符合二元二次非线性关系。     

金属注射成形过程中的粉末堆积问题

本文综述了金属注射成形中颗粒及粉末堆积的研究状况，对双组元球形颗粒的数学模型的理论基础、基本概念和方法作了比较详细的介绍和分析，并扼要介绍了连续粒径分布的颗粒堆积和影响粉末—粘结剂的装载量大小的因素。     

Highly filled particulate thermoplastic composites: Part I Packing density of irregularly shaped particles

The packing density of irregular shaped particles greatly affects the properties of highly filled particulate composite materials. The effects of particle size distribution parameters on the packing density of fused silica powder and cristobalite flour powder of different size ranges is reported. Various size distributions, according to the log-normal function, were prepared by sieving and characterized by light scattering, using a Malvern 2600 light scattering instrument. The apparent and tap density of the various powders was used to characterize the packing density. The size distribution width was found to have a major effect on the packing density. In addition, the particle size was found to affect the packing density however, its significance depends on the size range and shape of the particles. Mixtures of powders, each having a different size distribution, behave differently. This revised version was published online in November 2006 with corrections to the Cover Date.     

Computer simulation of morphology and packing behaviour of irregular particles, for predicting apparent powder densities

This paper describes a methodology for prediction of powder packing densities which employs a new approach, designated as random sphere construction (RSC), for modelling the shape of irregular particles such as those produced by water atomization of iron. The approach involves modelling an irregular particle as a sphere which incorporates smaller corner spheres located randomly at its surface. The RSC modelling technique has been combined with a previously developed particle packing algorithm (the random build algorithm), to provide a computer simulation of irregular particle packings. Analysis of the simulation output data has allowed relationships to be established between the particle modelling parameters employed by the RSC algorithm, and the density of the simulated packings. One such parameter is η, which is the number of corner spheres per particle. A relationship was established between η (which was found to have a profound influence on packing density), and the fractional density of the packing, fd. Vision system techniques were used to measure the irregularity of the simulated particles, and this was also related to η. These two relationships were then combined to provide a plot of fractional density for a simulated packing against irregularity of the simulated particles. A comparison was made of these simulated packing densities and observed particle packing densities for irregular particles, and a correlation coefficient of 0.96 was obtained. This relatively good correlation indicates that the models developed are able to realistically simulate packing densities for irregular particles. There are a considerable number of potential applications for such a model in powder metallurgy (PM), process control. In combination with on-line particle image analysis, the model could be used to automatically predict powder densities from particle morphology.     

Novel powder packing theory with bimodal particle size distribution-application in superalloy

Powder packing behavior plays an important role in determining sintering ability of powder and the resultant performance of materials. In this study, a novel powder packing theory with bimodal particle size distribution is proposed by considering the loosening effect, wall effect and wedging effect. This theory is applied in PM nickel base superalloy by using mixture of coarse particles and fine particles. Microstructures of alloy sintered by vacuum hot pressing (HP) are observed by optical microscope (OM) and electron backscatter diffraction (EBSD). The prediction result by this theory is in good agreement with the experimental results. The enhanced sintering ability of powder containing appropriate fractions of coarse particle and fine particle is ascribed to the filling of fine particles to the voids between coarse particles, which enhanced the density of sample after sintering. Tensile behavior and the fracture morphology of alloys with various particle distributions are analyzed in details, suggesting the higher reliability of the present theory.     

Preformulation: Effect of Moisture Content on Microcrystalline Cellulose (Avicel PH-302) and Its Consequences on Packing Performances

This study evaluates the influence of moisture content on the packing performances of a new grade of microcrystalline cellulose (MCC) (Avicel PH-302) either by classical method or by an unconventional compression technique (constant volume reduction of powder bed). An increase in moisture content decreases the apparent density of the powder bed, resulting from interparticulate friction enhancement. This modification of apparent density seems to be the main effect caused by the presence of humidity, which explains the variations of compression properties, like an increase of powder plasticity generally observed in the experimental conditions.     

Preformulation: Effect of Moisture Content on Microcrystalline Cellulose (Avicel PH-302) and Its Consequences on Packing Performances

This study evaluates the influence of moisture content on the packing performances of a new grade of microcrystalline cellulose (MCC) (Avicel PH-302) either by classical method or by an unconventional compression technique (constant volume reduction of powder bed). An increase in moisture content decreases the apparent density of the powder bed, resulting from interparticulate friction enhancement. This modification of apparent density seems to be the main effect caused by the presence of humidity, which explains the variations of compression properties, like an increase of powder plasticity generally observed in the experimental conditions.     

The role of rolling friction in granular packing

In order to study the effects of the rolling friction of the particles on granular packing, we present a detailed analysis of circular disk assemblies with the rolling friction under macroscopic one-dimensional compression. The rolling friction of the particles produces a resisting moment to the rolling at each contact. A series of 2-D DEM simulations are performed with various values for the rolling friction parameter. We focus on several macroscopic and microstructural properties of granular media and analyze them as a functions of the rolling friction. From these results, we show that the rolling resistance, which results from the rolling friction of the particles, contributes to the inhibition of the rearrangement of the particles and increases the magnitude of the fabric anisotropy under packing. In addition, from both microscopic and macroscopic points of view, we describe that the stress state in a granular packing can vary considerably depending on the rolling resistance.     

Low‐cycle fatigue behaviour of ductile closed‐cell aluminium alloy foams

This work investigates the fatigue response of a class of ductile closed‐cell aluminium alloy foams, known by their commercial name Alulight M8. In order to determine the yield stress of the used foams, preliminary experimental tests were performed, at room temperature, in monotonic compression on cylindrical specimens of 25 mm diameter and 25 mm height, with a loading speed of 10 mm/min. Fatigue tests were performed in uniaxial compression on cylindrical specimens (25 mm × 25 mm) with a stress ratio of R = 0.1, at a frequency of 10 Hz. The peak stress was varied from 110 to 135% of the yield stress in compression. Tested specimens were cut from the same cylindrical bar, and the density of the investigated material was 500 kg/m³ ± 10%, or a total of 18 specimens being investigated. With the gathered experimental data, S–N curve was generated, and the effect of cellular structure (e.g. structure irregularity–the number and the size of cells) being investigated and discussed.     

Constitutive modeling of powder metallurgy processed Al–4%Cu preforms during compression at elevated temperature

In this study, a hot deformation constitutive base analysis has been conducted on powder metallurgy (P/M) processed Al–4%Cu preforms. The main objective is to evaluate the effect of initial relative density on the hot deformation behaviour and to establish the constitutive equation which considers the effect of initial relative density during hot compression test. This has been carried out by using the true stress–true strain curve data obtained from hot compression test of P/M processed Al–4%Cu preforms with different initial relative density of 0.84, 0.87 and 0.9 for various range of temperature 300–500 °C and strain rate range of 0.1–0.4 s⁻¹. It has been found that the flow stress is notably influenced by initial relative density, temperature and strain rate. The results show that the flow stress exhibits peak value at certain strain value, and then decreases showing flow softening until the flow stress remains constant at higher strain values. A constitutive equation that predicts the flow stress in hot compression of P/M processed Al–4%Cu preforms has been developed. The predicted flow stress values are in a good agreement with the experimental results and it is confirmed that the formulated constitutive equation is accurate and reliable to predict the flow stress of Al–4%Cu preforms during hot compression at elevated temperature.