Micro and nanosized particles are found in many types of materials, including food additives, metals, polymers and catalysts. In an effort to formulate novel industrial, medical and scientific applications, researchers seek to characterize the mechanical, thermal and chemical properties of these particles.
A benchtop scanning electron microscope (or tabletop SEM) is used in industry and academia to characterize particles’ morphological, topographical, and chemical characteristics. They allow a precise determination of these characteristics while rendering stunning images of specimens.
Sample Preparation for a Benchtop SEM
Electron microscopy, including transmission electron microscopy (TEM) and scanning electron microscopy (SEM), is recognized as the gold standard for the characterization of particles at nanoscales (orders of 10-9 meters). Electron microscopes are versatile tools providing greater depths of field than optical microscopes, higher resolutions and a capacity to reveal chemical compositions when combined with a range of spectroscopy techniques.
Sample preparation is an essential part of an efficient workflow when using a benchtop SEM. The sample must typically be dried. For non-conductive materials, the sample may be coated with a nanometer-thick layer of conductive carbon or metal (such as gold) to prevent spurious charging while studying the sample. Once the sample has been prepared, it is placed in the analysis chamber of the benchtop SEM. Typically, analysis is performed in a vacuum, and users may employ cryogenic methods for the preparation of sensitive materials.
During operation of the benchtop SEM, a high-energy beam of electrons is scanned across the sample. Coaxial magnets focus the electron beam to a point as small as several nanometers in diameter. As the electron beam interacts with the sample’s surface, the signals generated are collected by various imaging and analytical detectors. Thus, high-resolution nanoscale images are formed and precise measurements are obtained.
Particle diameters and geometries may be studied in great detail. By utilizing several images together with software, the size distribution of particles may be determined and a concentration versus particle diameter may also be calculated. A tabletop SEM enables flexible approaches to the analysis of various types of particulates in semiconductors, powders for additive manufacturing, automotive cleanliness and polymers.
Particle Analysis Using a Benchtop SEM
The analysis of particle size is essential to the characterization of materials. This includes the identification of foreign substances, forensic examinations and quality control in additive manufacturing, automotive/aerospace cleanliness and pharmaceuticals.
In order to elucidate questions surrounding morphology, surface area and porosity, researchers have traditionally turned to light scattering, light obscuration or direct imaging techniques. While characterizing the size distribution of particles is essential, correlating this information with chemical composition offers valuable insights into the characteristics of materials. The combination of a benchtop SEM with energy-dispersive X-ray spectroscopy (EDS) is the ideal solution for integrating particle visualization and chemical composition analysis.
JEOL’s Particle Analysis Software 3 (PA3) has been integrated into its Benchtop SEM/EDS platform. It enhances the capabilities of a benchtop SEM by automating the detection, chemical analysis and classification of particles, grains and other features found in materials. As part of an efficient workflow, it provides fast, unattended measurements across sizeable areas of a sample or even multiple samples.
A typical workflow involves taking an optical image with an integrated Stage Navigation System camera. This image is used to quickly navigate regions of interest, simplifying the acquisition of benchtop SEM images and EDS spectra within an automated workflow. User-defined recipes may be utilized for specific use cases. These recipes streamline the setup, allowing less experienced users to execute a run. The software is also preloaded with materials-specific libraries such as the Metal Feature Analysis (MFA) Library, which complies with ISO 4967.
JEOL’s PA3 software has advanced functionalities for particle characterization, including probe tracking, using shape information to include or exclude particles from EDS analyses and different methods of stopping the run (by count, morphology or element). PA3 facilitates the identification and analysis significantly increasing the throughput of benchtop SEM/EDS-based characterization.
Benchtop SEM from JEOL
The benchtop SEM (and EDS) system from JEOL allows users to set up a compact and user-friendly lab environment without compromising data integrity. This efficient workflow guides the user from sample preparation to imaging, particle analysis and reporting.