Views: 0 Author: Site Editor Publish Time: 2026-06-26 Origin: Site
In powder processing, many manufacturers encounter the following problems:
Mixing time is already very long, yet uniformity remains poor.
Sampling results vary significantly from one location to another.
Product performance is inconsistent.
Ultrafine powders appear to contain a large number of coarse particles.
Mixing quality reaches a plateau and cannot be further improved.
These challenges are especially common in industries such as:
Lithium battery materials
Conductive additives
Carbon black
Graphene
Nanomaterials
Pharmaceutical powders
In many cases, the root cause is not the mixer itself, but a phenomenon that is often overlooked Pseudo-Particles
In modern powder engineering, pseudo-particles are considered one of the key factors affecting mixing uniformity, dispersion quality, and final product performance.
Understanding pseudo-particles is essential for understanding ultrafine powder processing and high-uniformity mixing.
Pseudo-particles are also known as:
Agglomerates
Secondary Particles
Particle Clusters
They are defined as large particle-like structures formed when multiple fine particles stick together through various interparticle forces.
Importantly, a pseudo-particle is not a true particle.
Instead, it consists of many smaller primary particles bonded together.
For example:
A primary particle size of 1 μm, may agglomerate into a cluster measuring 50 μm, 100 μm or even larger.
Although the cluster appears to be a single particle, it is actually composed of countless smaller particles.
Primary Particles
Primary particles are the original particles produced during material synthesis.
For example:
An alumina powder may consist of individual particles measuring 1 μm.
These represent the true particle size of the material.
Pseudo-Particles
Pseudo-particles are formed when many primary particles adhere together.
Their apparent size may reach:
10 μm
50 μm
100 μm
or even larger.
Therefore, the large particles you observe are not always true large particles.
Many are simply agglomerates of much smaller particles.
As particle size decreases, attractive forces between particles increase dramatically.
This is particularly true for Ultrafine Powders.
typically defined as powders smaller than 10 μm.
The finer the particles become, the greater their tendency to form agglomerates.
Van der Waals attraction is one of the most important causes of agglomeration.
As particle size decreases:
* Specific surface area increases
* Surface energy increases
As a result, particles naturally attract each other and form stable agglomerates.
During handling, conveying, and mixing:
Particles continuously rub against one another and equipment surfaces.
This can generate electrostatic charges.
Materials such as:
Carbon Black
Graphite
Fumed Silica
Nanopowders
are particularly prone to static buildup.
Electrostatically charged particles attract each other and form pseudo-particles.
Moisture present in the air can create tiny liquid bridges between particles.
These liquid bridges increase particle adhesion and strengthen agglomeration.
During storage, transportation, or packaging, powders may be subjected to pressure.
Compacted particles tend to form clusters and agglomerates.
Conductive Additives
Examples include:
Carbon Black
Super P
Conductive Carbon
Nanomaterials
Examples include:
Nano Alumina
Nano Silica
Nano Zirconia
Graphene
Due to its sheet-like structure, graphene tends to stack and agglomerate easily.
Carbon Nanotubes (CNTs)
CNTs are widely recognized as one of the most difficult materials to disperse.
Pharmaceutical Ultrafine Powders
Examples include:
Active Pharmaceutical Ingredients (APIs)
Micronized Drugs
Many people assume that mixing equipment handles individual particles.
In reality, mixers often process pseudo-particles rather than primary particles.
This creates several important problems.
Consider carbon black agglomerated into 100 μm clusters.
These agglomerates may appear evenly distributed throughout the mixture.
Visually, the mixture looks uniform.
However, the carbon black remains concentrated inside the agglomerates rather than being truly dispersed.
This phenomenon is known as False Uniformity.
The mixture appears homogeneous on a macro scale but remains non-uniform on a microscopic scale.
Pseudo-particles cannot participate effectively in the mixing process.
As a result:
Distribution becomes uneven
Sampling variability increases
Uniformity decreases
especially at the microscopic level.
In lithium battery manufacturing, for example:
Agglomerated CNTs may fail to form an effective conductive network.
This can lead to:
Increased electrical resistance
Reduced capacity
Shorter cycle life
Pseudo-particles are significantly larger than the primary particles from which they are formed.
Therefore, they are more susceptible to:
Particle Size Segregation
Density Segregation
which can cause the mixture to separate again after mixing.
Traditional equipment such as:
V-Blenders
Double Cone Mixers
Three-Dimensional Mixers
Two-Dimensional Mixers
primarily rely on Gravity Diffusion Mixing.
Materials are mixed through vessel rotation and particle repositioning.
However, the internal bonding forces within agglomerates can be relatively strong.
Simple tumbling action often cannot generate sufficient force to break them apart.
As a result, pseudo-particles may remain intact even after prolonged mixing.
In powder engineering:
Mixing and dispersion are not the same thing.
Mixing
Mixing refers to bringing different materials together and distributing them throughout a system.
Dispersion
Dispersion refers to breaking agglomerates apart and restoring individual primary particles.
For ultrafine powders:
Dispersion is often more important than mixing.
Because if pseudo-particles remain intact, even a visually uniform mixture may only exhibit false uniformity.
Several methods are commonly used.
If the measured particle size is significantly larger than the known primary particle size, agglomeration is likely present.
Scanning Electron Microscopy (SEM) can directly reveal agglomerate structures.
Unexpectedly large particles often indicate pseudo-particle formation.
Problems such as:
Reduced conductivity
Lower reaction efficiency
Poor mixing consistency
may all be linked to pseudo-particles.
With the rapid growth of advanced materials and new energy industries, more products rely on:
Ultrafine powders
Nanopowders
Conductive additives
CNTs
Graphene
For these materials:
The greatest challenge is often not mixing, but deagglomeration.
As a result, powder mixing technology is evolving from:
"Mixing Materials" to "Controlling Particle States"
Modern systems increasingly emphasize:
Dispersion capability
Shear intensity
Agglomerate breakup efficiency
Micro-scale uniformity
rather than simple bulk material movement.
Pseudo-particles are secondary particles formed by the agglomeration of many primary particles.
Their formation is mainly caused by:
Van der Waals forces
Electrostatic attraction
Capillary forces
Mechanical compaction
Pseudo-particles can lead to:
False uniformity
Poor dispersion
Reduced product performance
Increased segregation
Therefore, in ultrafine powder processing, the biggest challenge is often not mixing the materials together, but breaking pseudo-particles apart.
True high-quality powder mixing requires not only blending materials, but also achieving genuine particle-level dispersion.
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