粉体颗粒流动性的分形维测试法

粉体颗粒粒度分布分形维能很好的表征颗粒群粒度分布.本文通过建立数字显微颗粒粒度分布分形维数值的数学模型,探讨粉体流动参数与颗粒粒度分布分形维数值间的关系,确认颗粒粒度分布分形维数值可以用于表征粉体流动性,形成了可靠和简洁的粉体流动性能测定新方法.     

粉煤灰粉体颗粒细度与分维数研究

利用分形几何学原理研究粉煤灰粉体颗粒,探讨了粉煤灰粉体粒度的分布特征,测试、计算了相应的分形维数,研究表明：（1）粉煤灰粉体颗粒粒度分布都表现出分形分布,粉体粒度分布的分维值1〈D〈3;（2）粉煤灰粉体颗粒的分维值越大,其细度比和细度模数越小,其形态系数随之增大;（3）粉煤灰粉体颗粒的分维数与需水量比的关系成曲线关系,大致在分维值2以下时,其需水量比逐渐增大;但分维值大于2以后,其需水量比逐渐下降。     

转炉钢渣粉粒度分布的分形特征

采用Mastersizer2000激光衍射粒度分析仪对球磨转炉钢渣粉粒度分布进行了测试,运用分形几何理论分析了钢渣粉的分形维数,探讨了分形维数与球磨时间、比表面积、特征粒径、均匀性系数及胶砂性能之间的关系.结果显示:球磨转炉钢渣粉粒度分布具有分形特征;分形维数在2.2～2.5之间,其值大小反映了钢渣粉的细度和分布宽度;分形维数越大,钢渣粉越细,粒度分布越宽;分形维数与球磨时间、比表面积、特征粒径、均匀性系数以及胶砂(w(标准水泥)∶w(钢渣)=70∶30)流动度之间存在良好的线性相关,相关系数在0.95～1之间.在本实验条件下,存在一个最佳分形维数2.41,在此分形维数下砂浆各龄期抗压强度最高.     

机械力活化对钢渣粒度分布和胶凝性能的影响

测试了不同粉磨时间的钢渣的粒度分布,计算了钢渣粉粒度分布的分形维数,并研究了其与比表面积、粉体活性的关系.结果表明:粉磨时间增加,钢渣粉粒度变小,小颗粒所占比逐步提升,粒度分布的分形维数也随之增大,粉磨一定时间后,其粒度分布的分形维数增长速度趋于平缓.粒度分布的分形维数与颗粒的比表面积、水化反应活性线性正相关.机械力活化能够激发钢渣的胶凝性能.钢渣胶凝材料的水化产物以钙矾石(AFt)和水化硅酸钙(C-S-H)凝胶为主.     

水泥颗粒粒度分布分形维与其胶砂抗压强度的关系研究

为研究水泥颗粒粒度分布分形维与其胶砂抗压强度的关系,利用粒度分布分形维的计算模型分析了有关文献报道的10种水泥颗粒粒度分布分形维值,结果表明:定量表征其分形特征的分形维值在2.325～2.435之间,各水泥颗粒粒度分布具有分形特征;分析了水泥颗粒粒度分布分形维值与水泥3d抗压强度、28d抗压强度的关系,分析表明:化学组成和矿物组成基本相同的条件下,水泥颗粒粒度分布分形维与水泥胶砂的3d、28d抗压强度具有较好的正线性相关关系。     

重介质旋流器分选效果与入选原煤粒度组成的关系研究

介绍了分形维数的概念,采用分形维数表征原煤的粒度组成,实例研究表明,重介质旋流器分选效果与原煤粒度组成即分形维数之间存在着明显的线性关系,粒度组成越细,分形维数越大,分选效果越差,可能偏差越大。     

用于选择性激光烧结成型的聚酰胺6/硫酸钙复合粉体的制备及性能研究

采用溶液沉淀法制备了聚酰胺6/硫酸钙（PA6/CaSO₄）复合粉体,通过扫描电子显微镜（SEM）、差示扫描量热仪（DSC）、激光粒度分布仪和Ｘ射线衍射仪（XRD）对复合粉体的微观形貌、热性能、粒度分布、晶体结构和流动性进行了表征。结果表明,随着CaSO₄的加入,PA6/CaSO₄复合粉体由松散的球形结构转变为密实的球形结构;CaSO₄的加入能够提高PA6/CaSO₄复合粉体的结晶度并拓宽其烧结温度窗口,在CaSO₄含量为5 %（质量分数,下同）时,结晶度和烧结温度窗口均达到最大值,分别为61.84 %和18.95 ℃;PA6/CaSO₄复合粉体的粒径随CaSO₄含量的增加呈现先减后增的趋势,休止角先减后增,堆积密度先增后减;当CaSO₄含量为3 %~5 %时,PA6/CaSO₄复合粉体的流动性能最佳,最适用于选择性激光烧结。     

低温状态下废旧电路板的破碎粒度及产率分析

利用自行搭建的系统进行了废旧印刷电路板的细碎实验,分析了不同冷却温度、破碎时间、破碎机转速、刀具间隙、排料尺寸对废旧电路板物料粒度分布与产率的影响,并采用正交实验优化了细碎机的工艺参数. 结果表明,冷却温度为-30℃时粒径0.5~1.4 mm的合格产品产率较高,为43.8%,产物粒度分形维数最小,为1.94,粒度分布规则;不同破碎时间的产物粒度分形维数变化不大. 正交实验结果表明,破碎时间越长越有利于提高产率,提高产率需减小刀具间隙、提高破碎转速,最佳破碎时间为10 min,刀具间隙不小于3 mm.     

颗粒群粒度分布宽度表示方法的研究

总结了传统的粒度分布宽度的表示方法,分析了它们的适用场合。通过理论推导,提出了一种表示粒度分布宽度的新方法--颗粒群的分形维数。颗粒群的分形维数D可定量描述粒度分布宽度。分形维数D越大,颗粒群的粒度分布越宽。     

铝-空气电池废电解液制备片状氧化铝的研究

以铝-空气电池废电解液为原材料,用硫酸铝调节pH值,用硫酸钾作为熔盐制备片状氧化铝(α-Al₂O₃),研究了合成温度、晶种添加量对α-Al₂O₃粉体体积分数、粒度大小及粒度分布的影响规律。通过X射线衍射仪、扫描电子显微镜和激光粒度仪等,对加入不同晶种量的α-Al₂O₃粉体的结构和形貌进行表征。结果表明,添加晶种后可以提高α-Al₂O₃粉体的体积分数,减小α-Al₂O₃粉体的粒度,使α-Al₂O₃粉体的粒度分布更集中,同时使α-Al₂O₃粉体更分散。此外,当晶种添加量为5%(质量分数)时,制备出的片状α-Al₂O₃的体积分数可达97.0%,平均粒度约为7.24μm。     

水泥粉体流动行为及其与不同材质库壁粘附性研究

水泥粉体流动性与其储存、输送、给料、混合等操作密切相关.通过休止角、内摩擦角、粘聚力和无侧限抗压强度测试方法,研究了含水率对水泥粉体流动性的影响,对比了水泥粉体与砂浆、钢、涂料、防腐卷材四种壁面材料的壁摩擦角和附着力.结果表明:随着水泥粉体含水率增加,休止角、粘聚力和无侧限抗压强度增加,水泥粉体流动性变差.松散堆积水泥...     

The effect of surface modification of aluminum powder on its flowability, combustion and reactivity

Surface modification of aluminum powders for the purpose of flow improvement was performed and several samples were prepared. Correlations between the flowability and reactivity for these powders as well as for the initial untreated aluminum powder were established. The powders were characterized using Scanning Electron Microscope (SEM), particle size distribution, angle of repose flowability test, Constant Volume Explosion (CVE) combustion test, and Thermo-Gravimetric Analysis (TGA). The surface modification of micron-sized aluminum powders was done by: (1) dry coating nano-particles of silica, titania and carbon black onto the surface of spherical aluminum powders and (2) chemically and physically altering the surface properties of the same powders with methyltrichlorosilane. All surface modifications improved flowability of the powders. CVE measurements indicate that powders with an improved flowability exhibit improved combustion characteristics if the powder treatment does not add an inert component to aluminum. The TGA results do not show significant differences in the reactivity of various powders. Based on combined flowability and CVE characteristics, the silane modified material gave the best results followed by the powders dry coated with carbon, titania and silica, respectively.     

PVC干混料粉体流动性的影响因素

介绍了与粉体流动性有关的理论,分析了PVC树脂、CPE、碳酸钙和冷混工艺对PVC干混料粉体流动性的影响,结果表明:①乙烯法PVC树脂的粉体流动性一般优于电石法PVC树脂,且波动较小;②某些厂家的冲击改性剂CPE可改善PVC干混料的粉体流动性,并且随着CPE用量的增加,PVC干混料的粉体流动性增加;③不同生产厂家的PVC/CPE体系对PVC干混料粉体流动性的影响规律不同,应不断摸索,找出最佳组合;④随着碳酸钙用量的增加,PVC干混料的粉体流动性降低,特别是在料斗上的表现更为突出;⑤充分冷却后的PVC干混料粉体流动性较好。     

Einfluss der Partikelgröße und Partikelform auf das Fließverhalten von kommerziellen Magermilchpulvern

Because of the numerous application as food ingredient skim milk powder is of prime economically importance among milk powders in Germany. However, the ease of powder handling, which is determined by the flow properties, is often not regarded as a real quality attribute. To better understand the powder handling characteristic of skim milk powders this work deals with flowability measurement of commercial skim milk powders by using shear cell testing technique. Furthermore relationships between particle size, particle shape and flowability data are highlighted.     

Preparation of spherical WC-Co powder by spray granulation combined with radio frequency induction plasma spheroidization

In this paper, spray granulation and radio frequency plasma spheroidization were used to obtain spherical WC-Co powder for laser powder bed fusion from mixed WC and Co powder. The effects of solid content and polyvinyl alcohol content of the slurry on granulated powder were studied. Then the spheroidization effects of different granulated WC-Co powders were investigated and compared. Results show that the granulated powder obtained from the slurry with solid content of 65 wt% and polyvinyl alcohol content of 2.5 wt% has the best performance after plasma spheroidization, whose flowability and apparent density are 10.20 s/50g and 6.76 g/cm³, respectively. Moreover, W and C distribute uniformly in the spheroidized WC-Co powder while the Co element is mainly distributed in the gaps of tungsten carbide. It is also noted that W₂C, free carbon and Co₃W₃C appear in the spheroidized WC-Co powders due to the decomposition of WC during the plasma spheroidization process. Furthermore, the decomposition of WC-Co powder particles with smaller size is more serious, which leads to the presence of black and white particles with significantly different carbon content distribution in the spheroidized powder.     

超细滑石粉填充PP的增强效应

以偶联剂改性的超细滑石粉填充PP制备复合材料，测定了复合材料的力学性能，分析了偶联剂的种类，滑石粉细度和填充量对PP/滑石粉性能的影响，考察了体系动态粘度的变化规律。计算了滑石粉与PP间的粘附功。研究表明粘附功与滑石粉的增强性能之间有良好的对应关系。     

Modified solution combustion route for the preparation of plasma sprayable ceria powder

Plasma sprayable grade ceria powder was prepared by the solution combustion method. This is the first report on the application of solution combustion for the synthesis of plasma sprayable grade oxide powders. The fuels and fuel ratios used in the solution combustion were modified to achieve adequate flowability. It was found that when a mixture of fuels like glycine and ammonium acetate was used, the combustion process yielded larger agglomerates. Phase purity of the powders was confirmed by powder XRD. The morphology of the particles was determined by scanning electron microscopy.     

分形理论在耐火材料生产中的应用

介绍了分形理论在耐火材料生产过程中的应用 ,提出 :(1)在耐火材料破粉碎工序之前加一个冷却处理工序 ,应用分形理论研究矿石碎裂机制 ,可提高耐火原材料尤其是硬质耐火原料的破粉碎效率 ;(2 )研究粉体颗粒的分形结构 ,既可以预测超微粉体的流动性 ,也可以预测粉体在压制过程中的充填状况 ,从而改良粉体的制备、存储、输送和运输等过程 ;(3)建立受压状态下矿石的分形裂纹结构、矿石构造特征以及施加给矿石的应力应变方式这三者之间的联系 ,对完善磨矿工序中的前馈质量控制有帮助 ;(4 )确定分形级配的颗粒配比 ,将有利于提高材料的性能 ;(5 )在耐火材料中添加分形结构的弥散粒子或纤维 ,能有效提高耐火材料的强度和韧性 ;(6 )加强吸入粉尘分形结构研究 ,防治耐火材料行业的职业病。     

氧化铝微粉与减水剂对刚玉质浇注料施工性能的影响

研究了减水剂(包括六偏磷酸钠和萘系、三聚氰胺类及聚羧酸盐类3类减水剂)、氧化铝微粉(包括烧结氧化铝微粉和活性氧化铝微粉)对纯铝酸钙水泥结合刚玉质浇注料的流动性能和力学性能的影响。结果表明:1)氧化铝微粉的平均粒度对浇注料的流动度有较大的影响,在一定范围内,粒度越粗,浇注料的初始流动性越小,可工作时间越短。2)氧化铝微粉中可溶性碱性氧化物的含量对浇注料的施工性能和可工作时间有一定的影响。3)减水剂既影响浇注料的需水性,还影响浇注料的强度发展,必要时需引入缓凝剂或者促硬剂进行调节。4)综合比较萘系、三聚氰胺类及聚羧酸盐类3类减水剂,以聚羧酸盐类减水剂的减水效果较好。     

Compaction and Sintering Behavior of Bimodal Alumina Powder Suspensions by Pressure Filtration

The compaction behavior of fine alumina powders with different particle sizes or bimodal particle-size distributions that are undergoing pressure filtration was investigated. Three alumina powders—average particle sizes of 0.2—0.86 μm—were compacted to a solids fraction of 62—65 vol% from suspensions at pH 3, which was the pH level at which the suspensions showed their lowest viscosity. When the powders of different average sizes were mixed, the suspensions showed better flowability, and the lowest viscosity was obtained when the fraction of fines was ∼30 vol% and pH = 3. The mixed-sized powder suspensions were compacted to higher density than the suspensions of unmixed fine or coarse powders, and the maximum density was obtained for mixed suspensions that had the lowest viscosity, despite the different particle-size ratio. Maximum densities of 72.5% and 75.0% were attained when the size ratios were 2 and 5, respectively. The compacts that were pressure-filtered from mixed suspensions exhibited a single-peaked pore-size distribution and a homogeneous microstructure, whereas the pore-size distributions of dry-pressed compacts were double-peaked. The sintering behavior of the compacts that were pressure-filtrated from bimodal powders exhibited significantly better sinterability and much-less linear shrinkage than the coarser powders and the dry-pressed powder compacts.