Particle Size vs. Particle Shape: Why Sieve Analysis Is Only the Starting Point

In powder procurement and quality control, particle size is often the first metric written into a specification. Once the powder passes through the sieve, falls into the specified size fraction, and the report shows "Pass," the process for many stops there.

But here is the question: Does particle size compliance truly equal powder performance compliance?

A recent 2026 study on commercial nickel powders by a South Korean research team, published in the Journal of Powder Materials, offers a blunt reminder: Not necessarily. The researchers compared spherical and dendritic nickel powders, further dividing each morphology into two sieve classes: 25–32 μm and 32–45 μm. They found that within the tested sample groups, changing the sieve classification had a relatively limited impact on resistivity, while the difference in electrical behavior between the spherical and dendritic groups was striking. Under matched pressure conditions, the reported resistivity values differed by a factor of approximately 16 to 70, depending on the pressure conditions and sample pairs.

This is not to say sieving is unimportant. Sieving is, of course, crucial—it is a fundamental tool for particle size control. But it answers a very narrow question: Can this powder pass through this sieve aperture, and which size fraction does it fall into? It does not answer whether the particles are spherical or dendritic, whether the surface is oxidized, whether the supplier's process is consistent, and it certainly does not answer how this powder will actually perform in pressure-conductive rubber.

The Core Pain Point of Sieve Reports: It Looks Too Much Like a "Complete Answer"

Sieving analysis is highly practical in the lab. It can tell you:

• The mass retained on each sieve aperture;

• The proportion of material within the specified size fraction;

• The presence of oversized particles;

• Whether there are variations in particle size distribution between batches;

• Whether the powder meets sieve-based acceptance criteria.

This information is valuable. The problem is that many procurement and quality processes equate "meeting sieve acceptance criteria" directly with "stable powder quality." This is a dangerous leap.

Powders within the same sieve class can be completely different in the following aspects:

• Particle morphology: spherical, dendritic, irregular, or flake-like;

• Surface structure: roughness, oxide layer, surface treatment;

• Inter-particle contact mode: point contact, surface contact, branched interlocking;

• Specific surface area and flowability;

• Resistivity, filling behavior, or processing performance in actual applications.

A sieve report won't tell you these things. It cannot independently determine whether particles are spherical or dendritic, cannot quantify surface roughness, cannot identify surface oxidation, and cannot measure resistivity. Using sieve analysis for these tasks is like using a bathroom scale to judge a person's health—weight matters, but it’s not the whole story.

What's Really Striking About This South Korean Nickel Powder Study: Same Sieve Class, Performance Can Differ by an Order of Magnitude

The study focused on nickel powders used in pressure-conductive rubber semiconductor test sockets. The researchers compared four commercial nickel powder samples with two morphologies: spherical and dendritic; each morphology was further divided into two sieve classes: 25–32 μm and 32–45 μm. They evaluated particle size distribution, surface area, true density, particle morphology, and resistivity under different compression pressures.

The results are clear: within the tested sample groups, sieve class variation had a relatively limited impact on resistivity, while the difference between the spherical and dendritic groups was very large. Dendritic powders exhibited lower resistivity or formed effective conductive contacts earlier at lower compression pressures; under matched pressure conditions, the resistivity of the two groups differed by a factor of approximately 16 to 70.

A crucial caveat must be stated: the spherical and dendritic powders came from different suppliers. Therefore, this difference is a combined effect of morphology and supplier factors, and cannot prove that particle morphology alone caused all the differences. The supplier's manufacturing process, surface state, impurity control, and oxidation degree may all play a role.

But it is precisely this caveat that makes the conclusion even more impactful for procurement and quality control: the sieve report you receive doesn't even cover the variables that truly affect performance—"morphology + supplier + surface state." Particle size compliance might just be "looking compliant."

Even More Provocative: Sieve and Laser Diffraction Results Might Naturally Be Inconsistent

The study includes an interesting detail. The researchers first separated the nickel powder into a 25–32 μm sieve class, then measured the particle size distribution using laser diffraction. The reported laser diffraction D50 values for the spherical and dendritic samples were approximately 34.9 μm and 35.5 μm, respectively.

At first glance, this seems contradictory to the sieve class. But it’s not that sieving must be wrong; rather, the two methods measure different things. Mechanical sieving looks at whether a particle can pass through a sieve aperture under specified conditions; for non-spherical particles, passage depends on the effective cross-section and orientation. Laser diffraction calculates an equivalent spherical diameter; an elongated or branched particle might pass through a sieve aperture in a favorable orientation but yield a larger equivalent spherical diameter in laser diffraction. D50 is the median equivalent spherical diameter, not the sieve upper limit.

Therefore, inconsistency between sieve and laser diffraction results does not automatically mean a testing error. It just reminds you that different measurement principles answer different questions. For powder engineers, when comparing supplier reports, if the particle size analysis methods differ, directly comparing the numbers is risky.

What Sieve Analysis Should and Should Not Do

Sieve analysis should continue to be done, and done well. It is a fundamental tool for laboratory particle size analysis and quality control. But it should not be treated as a complete evaluation of powder performance.

Sieve analysis confirms particle size distribution and sieve residue; it cannot replace SEM for morphology, image analysis for shape quantification, surface analysis for oxidation, or application testing for resistivity, flowability, or filling behavior.

A more reasonable powder evaluation workflow should be divided into three layers:

1. Particle Size Classification: Use test sieves and controlled screening procedures to confirm size fractions, retained mass, and oversized particles.

2. Particle Morphology: Use microscopy or image analysis to check if particles are spherical, dendritic, or irregular, and whether the surface structure is consistent.

3. Application-Specific Performance: Directly measure metrics relevant to the application scenario, such as resistivity, flowability, surface area, and chemical composition.

Not every powder requires all three layers. But if your application is sensitive to morphology, contact structure, or electrical conductivity, looking only at a sieve report is far from enough.

The Role of Laboratory Sieve Shakers: Do Particle Size Control Solidly, But Don't Make It Take the Blame It Shouldn't

For laboratories handling metal powders, chemical powders, pharmaceutical materials, and advanced materials, laboratory sieve shakers remain core equipment for particle size control. Compared to manual sieving, programmable laboratory sieve shakers standardize mechanical motion, operating time, and testing procedures, making sieve results between batches more comparable.

LVOBO laboratory sieve shakers, including the BO-200SY and BO-300SY models, are designed for laboratory particle size analysis, powder classification, and sieve residue testing. Selected configurations offer programmable screening functions such as forward/reverse motion, vertical vibration control, operating time and cycle settings, and storage for multiple test programs; specific functions depend on the configuration.

But the equipment's role must be clearly stated: a sieve shaker determines how material passes through selected apertures; it does not replace SEM, image analysis, surface analysis, or resistivity testing. It is the starting point of particle size control, not the endpoint of powder quality. Using the sieve shaker correctly means controlling the particle size variable; treating the sieve report as a complete quality conclusion leaves the risk to downstream processes.

Conclusion: Particle Size Compliance is Just the Starting Point, Not the Endpoint

The core takeaway from this South Korean nickel powder study for procurement engineers, R&D teams, and quality control labs is: powders within the same sieve class can still exhibit significantly different behaviors in specific applications. And because morphology and supplier factors were confounded in the study, this result serves more as a warning: do not treat a sieve class as a complete quality description, and do not assume a sieve report covers morphology, surface state, and supplier consistency.

So, to put it boldly:

Sieve analysis is a must, but judging powder quality solely by sieve analysis is like using one ruler to measure an entire material system.

Use sieving to control particle size, use microscopy and image analysis to examine morphology, and use application testing to evaluate actual performance. Reliable powder quality control is not about buying more instruments; it's about understanding exactly what questions each method can and cannot answer.

Particle size compliance is just the starting point. True powder quality lies beyond the sieve apertures.