ball milling description

Ball milling
Attrition milling
Ball milling
Milling parameters(粉碎参数)
• Type of mill (ball, attritor, planetary or vibratory mill), (种类有ball,
attritor, planetary 和 vibratory.) • Intensity of milling (rpm), energy input(输入的能量) • Milling atmosphere (air or inert atmosphere), (操作环境) • Ball-to powder weight ratio (BPR),(球磨球和粉末的重量比) • Filling rate (填充速率) • Milling temperature(粉碎温度) • Wet or dry(干或湿操作环境) • Small amounts of additives, so called process control agents (PCA), are commonly used during milling to prevent excessive cold welding of powder on other powder particles or onto the balls and milling container. The addition of a PCA such as ethyl acetate or stearic acid also enhances the recovery of the powder from the mill. 需要加过程控制媒介,用于防止 粉末颗粒间，粉末颗粒和球磨球，粉末颗粒和容器壁间的机械粘结
from the mechanical forces, thus milling to less than a mean size of about 5 µm is difficult. (由于小颗粒会形成保护屏蔽，颗粒最小只能达到5um)
• Efficient to break up agglomerated powders and for powder mixing !(可有
?crushingofspongelikeproducts粉碎海绵状颗粒?brittlematerialsandalloyssbbialmgalloysintermetallics粉碎脆性材料和合金粉碎脆性材料和合金?productionofdenseorflakepowders生产高密度薄片状粉末?crushingofatomisedpowder粉碎雾化粉末?raremetalsbeorcompoundssuchashydridesofrefractorymetalstih2wherethepowderneedstobeprocessedinanisolatedwaytoxicityorunderprotectiveatmosphereoxidation生产对加工条件有特殊要求的稀有金属和聚合物comprisesallprocessesinwhichmaterialsarereducedinparticlesizecomminutionorattrition?themostcommonprocessforcomminution
1. Mechanical processes
comprises all processes in which materials are reduced in particle size (= comminution or attrition)
Problems involved in metal powder milling 高能球磨缺点:
All these parameters need to be optimised as a function of the specific powder !
对于不同种类的粉末，上述参数需要通过实验获得最优值
Ball milling
All parameters need optimisation !
Is however used for (广泛应用于):
• Crushing of sponge like products粉碎海绵状颗粒 • Brittle materials and alloys (Sb, Bi, Al-Mg alloys, intermetallics)粉碎脆 性材料和合金 • Production of dense or flake powders生产高密度薄片状粉末 • Crushing of atomised powder粉碎雾化粉末 • Rare metals (Be) or compounds (such as hydrides of refractory metals (TiH2)) where the powder neetoxicity) or under protective atmosphere (oxidation)
Usually not the most economic process for metals(不经济) Difficult due to ductility and plasticity of most metals(不易用于延展性好的金属中) Oxydation of metal when milling in air (在空气中球磨，易氧化)
生产对加工条件有特殊要求的稀有金属和聚合物
1.1. Ball milling
• The most common process for comminution.(最广泛使用) • A ball-mill is simply a cylindrical steel drum, lined with a wear-resistant
air-atomised Al-17Si-5Fe-3.5Cu1.1Mg-0.6Zr (wt %) starting powder
Ball milling
Milled ductile metal粉碎后的塑性金属 Ball-milled Cu(铜) en Al(铝)
material, rotating on its axis(使用钢制圆柱桶，表面覆有仿磨材料，可绕其轴 旋转)
• Ball mills can be operated in batch or continuous mode and can be sized
to take a charge of less than a kg (lab sizes) to tons per hour.(可用于连续 或批次生产，生产数量可为kg到数ton)
效减少颗粒聚集，并利于粉末混合)
• Can be performed wet or dry (湿或干条件都可实现) • Milling balls can be a source of contamination(粉碎球可带来杂质) • Rotation speed is a crucial parameter(转速是主要控制参数)
Ball milling
Attritor mill
An attritor is a stirred media mill. A central shaft with rotating arms continually stirs a slurry of particles and spherical media. 不 停旋转的搅拌棒和球磨球同时存在 The stirred media mill is used industrially for wet grinding to below 1 µm and for the dispersion of agglomerates of submicron particles.可使颗粒度小到 1um，且可粉碎聚集物到 um 级 Mill capacities range from a few grams to several tons per hour. The intense milling action produces considerable heat, necessitating cooling of the mill wall. 产量可从 gram 到 tons，需要外置冷 却系统。 Attrition grinding is used for the production of submicron powders of hard oxides, carbides and nitrides. O 化物，C 化物和 N 化物，可用 Attition 实现 um 级的颗粒度 Attrition milling can also be performed in vacuum or under inert gas conditions.可实现真空或者惰性气体的生产环境 Higher shear forces than during ball-milling.产生比普通的球磨大的 切应力 Ideal for mixing and deagglomeration ! 最适于混合和聚集物的粉碎
Ball milling
Horizontal ball mills
Optimal milling configurations
Ball milling
Planetary ball mills and vibratory mills
c
a
b
Four-station planetary ball mill (a,b), arrangement of rotating vials on the disk in the ball mill (b), and vibratory mill (c).
• Ball-milling produces a wide distribution of particle sizes, typically from
100 to 1 µm. (生产出的颗粒度分布广泛，从100到1um)
• As fine particles build up in quantity they tend to protect large particles