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High Resolution Aerodynamic Particle Size Analysis

The Amherst Process Instruments, Inc. (API) Aerosizer Particle Size Analysis System is a high speed, high resolution, aerodynamic particle size analyzer for dry powders in the size range of 0.2 to 700 µm (Figure 1). The Aerosizer unit, located in the materials characterization laboratory, consists of an Aerosizer LD Sensor Unit, an API Aero-Disperser dry powder dispersion system fitted to the Aerosizer LD, a controller, and a vacuum pump. The Aerosizer LD is a dual laser beam optical sensor system for time-of-flight measurements and integral air flow control systems.

Figure 1: The Particle Size Analysis System consists of an Aerosizer LD Sensor Unit, an API Aero-Disperser dry powder dispersion system fitted to the Aerosizer LD, a controller, and a vacuum pump.

API Aero-Disperser Dry Powder Dispersion System has a microprocessor-controlled dry powder dispersing and sample feed system utilizes advanced fluidization, controlled de-agglomeration, and proprietary transonic flow dispersion technology to handle difficult powder dispersion applications. The system offers a simple, rapid, and reliable method of determining the particle size distributions of highly cohesive, as well as free flowing powders, without the need for costly and inconvenient solvents.

A powerful PC with integral math coprocessor and proprietary data acquisition boards performs the task of analyzing particle time-of-flight data using cross correlation techniques. In addition, the computer calculates and displays the measured particle size distribution.

The vacuum system pump is used to reduce the pressure in the sensor chamber to the appropriate low vacuum operating conditions. The Aerosizer system pump is equipped with a HEPA filter to collect the sample after analysis in order to prevent particles from entering the pump, as well as an oil de-mister at the pump exhaust.

The broad dynamic range of the Aerosizer makes it one of the most flexible analysis instruments available today. This equipment is beneficial to CAMMP due to the small amount of sample needed to obtain a particle size distribution, the accuracy of the resulting report, and the ease and speed of running the samples. Figure 2 shows an example of an output report comparing terrestrially- and microgravity-grown ZSM-5 zeolite samples.

Figure 2: Particle size distributions of high-silica ZSM-5 zeolite grown from untreated silica gel: (solid square) flight and (open square) terrestrial/control (Warzywoda et al., Microporous and Mesoporous Materials, 2000, 38: 423-432).