Bulk Solids Characterization

Triboelectric separation turns contact electrification from a handling hazard into a deliberate sorting mechanism. This article covers how material pairs are selected by charge polarity, what feed moisture and particle size do to separation efficiency, and where the technique sits relative to density and optical sorting.

FDA's proposed hub-and-spoke registration rule treats geographically separate manufacturing units as one establishment. The registration paperwork is new; proving that blend uniformity, granulation endpoints, and moisture behavior actually match between sites is the older, harder problem.

Gas pycnometry and BET surface area each report a single number. X-ray micro-CT builds a three-dimensional map of the pore network, showing connectivity, tortuosity, and closed porosity that single-value tests cannot resolve, within real resolution and sample-size limits.

AIR7359 explains why AMS-AM metal powder feedstock specifications leave certain properties uncontrolled, citing limited applicability and immature standardized inspection methods, and what that gap means for aerospace AM qualification programs.

Powder spreading in powder bed fusion is a recoater-powder interaction shaped by cohesion, particle size distribution, and particle shape. This article maps streaking, short-feeding, and layer non-uniformity back to their underlying mechanisms and separates powder-driven causes from blade wear and spreading speed.

Dynamic and aerated powder testing measures basic flow energy and specific energy to fill the gap between shear cell consolidation data and Hausner ratio screening, particularly for fluidized processing and rapid-refill feeding.

Single-contact electrification apparatus measures charge transfer from one controlled particle-surface or particle-particle contact, isolating a variable that bulk triboelectric and charge decay measurements can only report as an average.

Two lots that pass the same incoming flowability spec can still granulate differently after roller compaction. The reason usually traces to ribbon density, which responds to roll force, gap width, and feed screw speed as an interacting set, not to roll pressure in isolation.

Dense-phase and dilute-phase pneumatic conveying create different particle contact mechanics, and the resulting attrition and segregation risk depends on velocity, solids loading ratio, and the powder's own attrition sensitivity, not on a fixed assumption about which mode is gentler.

Cement fineness is not a single number. Blaine surface area, particle size distribution, grinding aid chemistry, and moisture history each pull on hydration reactivity in different ways, and a fineness specification that ignores any one of them will eventually let a bad batch through.

Geldart classification, minimum fluidization velocity, bubble dynamics, droplet-to-particle size ratio, and permeability all determine whether a fluidized bed process delivers controlled granule growth, uniform coating, or consistent drying at production scale.

Both the Hausner Ratio and Carr Index reduce bulk and tapped density to a single number. The mechanism behind that number, whether aeration, particle shape, or surface cohesion, determines whether it supports a process decision or actively misleads one.