Particle sizing techniques have advanced significantly throughout the past several decades. One of the most important contributions to this field is the application of laser-based technologies, complemented with the use of modern photo-detectors and digital computers. For some time, progress in laser light scattering technology has led to faster analyses, but the quality of the measurement was limited, often due to inadequacies in the detector.

Recognizing this need for better detection capability, Micromeritics developed the Saturn DigiSizer, an instrument that employed a laser diode and modern charge-coupled device (CCD) detector to significantly improve the sensitivity, resolution, reproducibility, and repeatability of the laser light scattering particle sizing technique.

With the Saturn DigiSizer II, Micromeritics has again improved this particle size technique. Utilizing a state-of-the-art CCD detector containing over three million detector elements, Mie theory, and unique design and data reduction features, the Saturn DigiSizer II gives users an extremely high level of resolution and sensitivity not available in other laser particle sizing systems. The level of detail, accuracy, and resolution enables the extraction of all available information from the static light scattering pattern. Users can now measure the same material on multiple instruments located at different locations around the world and get the same, highly detailed size distribution measurement on each instrument. The Saturn DigiSizer II is fully automated and requires little operator intervention.

Advantages

Applications

Ceramics

Particle Size information helps to determine curing and bonding procedures, control pore structure, ensure adequate green body strength, and produce a final product of desired strength, texture, appearance, and density.

Paints and Coatings

The particle size distribution of the pigment or filler influences the porosity, gloss, texture, color, color saturation, brightness, solids content, and film adhesion properties. The resulting porosity can control application properties such as fluidity, drying or setting time, and film thickness.

Cosmetics

The appearance, application, and packaging of cosmetics are influenced by the particle size distribution of the base powders, such as talc, and the pigments used in coloring.

Abrasives

Performance of abrasives, either in powder form or after being attached to a backing, is dictated by the size distribution of the abrasive powder. Over-sized particles lead to scratching and gouging. Undersized particles may lead to clogging of the abrasive papers.

Catalysts

Flow properties of fluid-cracking catalysts depend upon the particle size distribution of the particles. Surface area and pore structure of acid catalysts and catalyst supports result from the particle size distribution of the particles that are used to produce them

Mining

Refining efficiency of materials is related strongly to the particle size distribution of the raw mineral. For products that are used without chemical change, the size of particles taken from the mine may be too large for final usage. Analyses performed on the extracted minerals will help determine the amount of size reduction needed once the product reaches the processing plant.

Saturn II DigiSizer Configurations

The Saturn DigiSizer II System

Includes many options that allow you to tailor your instrument according to your specific needs. Multiple sample dispersion system options, an automatic autosampler, and a device for removing dissolved gases from the suspension liquid are available and contribute to the versatility of the system. These options are all designed and manufactured with the same care and attention to detail that produced the Saturn DigiSizer.

Liquid Sample Handling Units

The Saturn DigiSizer II’s sample handling unit ensures that every sample will be correctly dispersed. Micromeritics’ patented, state-of-the-art liquid sample handling units (LSHU) work with the instrument software to assure that sample suspension is of the proper concentration. A continuous flow through the reservoir provides a mixing action sufficient to keep all sample material suspended and prevents the settling of particles.

The LSHU has several automated features such as a built-in ultrasonic probe, automatic liquid level control, particle concentration detection, and a sample circulation system that continuously maintains dispersion. Auto-dispersion and auto-dilution features monitor the sample’s concentration and add liquid as needed until optimum concentration is obtained.

To reduce the possibility of sample carryover between analyses, the LSHU has a patented reservoir rinse design. While other designs simply fill and empty the reservoir to rinse, the Saturn DigiSizer’s LSHU has a feature that sprays the reservoir walls as the fluid level recedes. This removes residue that otherwise might cling to the surface.

Standard Liquid Sample Handling Unit

The standard unit includes a reservoir that is adjustable between 590 to 690 mL of dispersed sample with a circulation pump rate of 5 – 19 L per minute. It can circulate particles from 0.04 to 2500 µm. The high flow rate better supports particles that have an inherently higher settling velocity. In addition, the higher system clearance helps to avoid attrition of the particles during circulation.

Applications:

• Coarse particles
• High-density particles
• Quantity of sample, liquid supply and/or waste disposal is not a problem

Low-Volume Liquid Sample Handling Unit

The low-volume unit includes a reservoir that is adjustable between 100 to 120 mL of dispersed sample with a circulation pump rate of 2 – 12 L per minute. It can circulate particles from 0.04 to 750 µm in diameter. The low-volume liquid sample handling unit reduces cost by using smaller amounts of sample, and reduces the expense of waste disposal.

Applications:

• Sample quantity is limited
• Supply of dispersion liquid is limited and/or expensive
• Dispersion liquid may be hazardous to use and/or make disposal difficult

Particle Size Sample Preparation Accessories:

MasterTech Autosampler

The MasterTech Autosampler provides assurance that all samples are prepared and analyzed exactly the same way. The MasterTech is designed to increase throughput, repeatability, and reproducibility while reducing operator involvement. Up to 18 samples can be queued to run sequentially and completely unattended, including automatic stirring or sonication prior to transfer to the analysis system. The Saturn DigiSizer II’s operating software controls the MasterTech, and information about dispersion is stored in the sample file for future reference.

The MasterTech features a powerful ultrasonic probe for sample dispersion. Power to the probe tip is adjustable and the driving circuit is self-tuning for maintaining efficient and consistent sonic energy levels. A front-panel digital readout lets you know when the desired power is reached, and that same power is applied each time the method is repeated.

The AquaPrep can prepare 10 liters of water in less than 2 hours (at standard temperature and pressure) and ensures that you obtain the most accurate representation possible of the particle size distribution in your sample.

Superior Data Reduction and Reporting

The Saturn DigiSizer II’s powerful, easy-to-use and versatile user interface provides all the convenient features you expect from a Windows-based program such as point-and-click menus, multitasking capability, copy to clipboard, and more. The familiar Windows format reduces the time required for training and eliminates the need for most off-line data manipulation, resulting in increased productivity. The analysis program is designed to operate in the Windows environment and includes wizards and intuitive screens enabling you to perform system operations quickly and efficiently.

In addition, Micromeritics’ confirm 21 CFR Part 11 software assists with compliance to FDA regulations. Combined with Micromeritics’ IQ and OQ services, the user can be assured that the Saturn DigiSizer II system is validated for accuracy, reliability, consistent performance, and provides safeguards to protect the integrity of analysis records. System access is limited to authorized individuals. Secure, computer-generated, time-stamped audit trails are integral parts of the software program.

Wide Range of Data Presentation Options With many instruments that employ the static light scattering technique, a final report of reduced data typically is the only output available. The Saturn DigiSizer II, however, allows you to access the raw data. For instance, an image of the scattering pattern (2-D and 3-D representations) can be displayed, or you can receive a 592-point intensity versus angle data report in tabular or graphical form. To allow a quick assessment of the fit of theoretical models to experimental data, you also can obtain an overlay plot of measured data calculated from Mie theory.

Reduction of Raw Data Based on Mie Theory Ensures Exceptional Data Quality

Micromeritics employs the Mie theory (or the operator can choose to use Fraunhofer for particles that are both large and opaque) to reduce experimental data using a well-published, non-negative least squares method. These theories describe light scattering via theoretical models. No modifications to the theory are made with the Saturn DigiSizer II, and no assumptions of modality or distribution type are used. This is made possible by the remarkably high resolution of the optical system allowing very narrow size classes to be used in fitting the data to Mie theory.

The application of Mie theory provides unambiguous size data. In addition to reporting the data, the Saturn DigiSizer II can generate a plot that shows how well experimental measurements compare with theoretical Mie calculations for the scattering pattern from the reported distribution.

Revolutionary Approach to Particle Sizing

CCDs were originally developed and used for high-sensitivity and high-resolution requirements of imaging for astronomy. The Saturn DigiSizer II captures the scattering pattern using a patented optical design that employs a CCD as the light detector. A high-definition digital representation of the scattering pattern, which contains all of the information required to determine the particle size distribution, is captured.

Micromeritics’ application of the CCD array eliminates the need for mechanical fine-tuning of optical alignment. The instrument is automatically aligned by re-mapping the CCD array so that the scattering angle assigned to each element is exact to less than 0.005 degree relative to the central, unscattered light beam. The Saturn DigiSizer II’s CCD array has more than three million detector elements. The resulting extremely high resolution makes it possible to detect subtle differences in the scattering patterns and, therefore, subtle differences in particle size distributions. These minute differences in sample particle size may indicate a manufacturing variance, corroborate or refute theoretical studies, or help explain natural processes. Higher resolution means greater knowledge about differences between samples.

Advanced design features enable the Saturn DigiSizer to measure a light scattering pattern over a broad range of scattering angles with a dynamic intensity range from 1 to 1×1010. Combined with the high angular resolution of the CCD, the detector system provides an effective resolution of several million pixels at different positions in the scattering pattern, each detecting minute variations in light intensity. The Saturn DigiSizer’s high resolution enables the instrument to detect extremely small variations in the scattering pattern that are not detected by lower resolution instruments. It is this high level of accuracy that allows the Saturn DigiSizer to provide more detailed and precise particle size information than laser diffraction particle sizing systems of conventional design

This basic system without the TPx option makes chemisorption and physisorption analyses affordable to even the most modestly funded laboratories. The instrument rapidly and accurately performs pulse chemisorption studies and surface area analyses. The ChemiSorb 2720 features one port dedicated to performing the sorption analysis and a second port designed for sample preparation. It also features a built-in cooling fan for the sample port, four carrier gas inlets, one prep gas inlet, and the optional capability to accommodate a mass spectrometer or other external detector attached at the exhaust port.

In addition to chemisorption experiments that include determining the percent metal dispersion, active metal area, crystallite size, and quantifying acid and base sites, a range of physisorption experiments including BET surface area, Langmuir surface area, and total pore volume can also be conducted. Hands-on calibration and dosing procedures make it an excellent teaching tool for gas-solid surface interaction studies.

The basic instrument (without the ChemiSoft TPx option) provides two ways to collect data: 1) via a front panel meter that may be calibrated to display gas volumes adsorbed onto or desorbed from a sample, and 2) by a chart recorder monitoring the analog output from the thermal conductivity detector.

The ChemiSorb 2750

Higher Precision and Versatility

The ChemiSorb 2750 (built upon the same design elements as the Chemisorb 2720) has been further enhanced with the addition of an injection loop for pulsing active gases on the catalyst and features an enhanced dual-port design that allows in-situ preparation and analysis of two samples. Its dual-function sample ports have the capability to be used as either an analysis port or a degas port, eliminating the need to move the sample. This requires less effort and reduces the chances of contaminating an activated sample from exposure to stray gases.

Performing different types of analyses is also easier. In addition to the four carrier gas inlets and three preparation gas inlets, a dedicated gas inlet for the pulse chemisorption gas has been added. Thus the increased number of ports provides a rapid method for gas change overs without the need to manually disconnect, reconnect, and purge gas lines; this further minimizes the risk of contamination and improves the ease of operation.

Added Capability – Optional ChemiSoft TPx System

Optional ChemiSoft TPx System (temperature-programmed controller and software) expands the capabilities of the ChemiSorb 2720 and 2750 to include temperature-programmed reactions, data archiving, and advanced data reduction and reporting options. Expanded physisorption capability includes multipoint BET surface area.

ChemiSorb 2720 / 2750 Applications

ChemiSorb Theory and Design

The Analytical Technique

The ChemiSorb 2720 and 2750 both utilize the dynamic (flowing gas) technique of analysis. The quantity of gas adsorbed from the gas stream by the sample is monitored by a downstream thermal conductivity detector (TCD). The temperature and pressure at which adsorption/desorption occurs is either known or monitored. The instruments can be used to study physical or chemical adsorption. Preparation usually is accomplished by flowing either an inert or chemically active gas over the sample. After preparation, another gas is selected for analysis. Prep and carrier gases typically used to allow both physical and chemical adsorption experiments are He, Ar, N2, He/N2mixtures, H2, and O2, some serving as both prep and carrier.

Chemical Adsorption

Any of a number of reactive gases such as anhydrous NH3, CO2, CO, H2, N2O, O2, and H2S can be used to react with the active surface. A series of injections of a known quantity of reactive gas is injected into an inert gas stream that passes through the bed of catalysts. Downstream from the reactor is a detector, which determines the quantity of reactive gas that is removed from each injection. Chemisorption tests ideally are made with the sample at a temperature such that only chemisorption occurs. The active surface of the sample is saturated when the detector indicates that the total quantity of subsequent injections passes through the sample bed without any loss. The sum of the injected quantity minus the quantity of gas that passed without adsorption equals the quantity adsorbed.

Unlike physical adsorption, the injected gas chemically adsorbs only on the active surface and not on the support. Thus, the number of gas molecules required to cover the active surface area, once determined, leads directly to the active surface area. Applying the stoichiometry factor for metal reaction yields the number of accessible atoms of active metal. Furthermore, using the total quantity of active metal per gram of catalyst material (determined from the manufacturing formula) leads to the determination of the percent dispersion of active metal. Using the information gathered plus the density of the metal, the size of the metal crystallite can be estimated if it is assumed that these particles have uniform geometry of known volume-to-area ratio.

Physical Adsorption

The surface area of granulated and powdered solids or porous materials is measured by determining the quantity of a gas required to form a monomolecular layer on a sample. Physical adsorption tests typically are performed at or near the boiling point of the adsorbate gas; N2 being most common with a liquid N2 bath being used to maintain the analysis temperature. Under these conditions, a nitrogen and helium mixture of 30 volume percent nitrogen achieves the partial pressure condition most favorable for the formation of a monolayer of adsorbed nitrogen at atmospheric pressure. Under such specific conditions, the area covered by each gas molecule is known within relatively narrow limits. The area of the sample is thus calculable directly from the number of adsorbed molecules, which is derived from the gas quantity at the prescribed conditions, and the area occupied by each. Additionally, atmospheric pressure and ice water temperature may establish appropriate conditions for an n-butane and helium mixture. Other gases at other conditions are also usable.

Chemisorption defined:

Chemical adsorption is an interaction much stronger than physical adsorption. In fact, the interaction is an actual chemical bond where electrons are shared between the gas and the solid surface. While physical adsorption takes place on all surfaces if temperature and pressure conditions are favorable, chemisorption only occurs on certain surfaces and only if these surfaces are clean. Chemisorption, unlike physisorption, ceases when the adsorbate can no longer make direct contact with the surface; it is therefore a single layer process.

ChemiSoft TPx Option

When the optional programmable furnace system and accompanying ChemiSoft TPxsoftware are added to the 2720 or the 2750, another category of chemical adsorption testing can be performed –—Temperature-programmed reactions reduction (TPR),oxidation (TPO), and desorption (TPD).

Temperature control is provided by a furnace that operates from ambient (20 °C) to 1100 °C, and is able to produce temperature ramps of up to 50 °C/min within the 20 to 500 °C range, 30 °C/min within the 500 to 750 °C range, and up to 10 °C/min in the 750 to 1100 °C range.  The furnace controller can be programmed to provide multiple ramps and soak times.

Temperature-programmed Chemisorption

Temperature-programmed chemisorption provides information about adsorption strength when a catalyst is at working condition or at an elevated temperature.TPD analyses determine the number, type,and strength of active sites available on the surface of a catalyst from measurement of the amount of gas desorbed at various temperatures. During a TPR analysis, a metaloxide is reacted with hydrogen to form a pure metal. TPR determines the number of reducible species present in the catalyst and reveals the temperature at which reduction occurs. TPO examines the extent to which a catalyst can be reoxidized and measures the degree of reduction of certain oxides.

ChemiSoft TPx Software

Included in the Temperature-Programmed Chemisorption option is Micromeritics’ChemiSoft software that can be used to simplify chemisorption and physisorption aswell as temperature-programmed analyses.The software tracks and records time, monitors and records the analytical temperature and detector output, creates and organizes data files, reduces collected data, and produces a variety of user-defined reports. Advanced peak integration capabilities assure reliable results.

With ChemiSoft, you can create and store standard sets of analysis conditions for guiding frequently performed analyses. Analysis and prep conditions also are reported to provide a record of the environment under which the reported data were collected; this also assures faithful repeating of an experiment if required. Cut-and-paste and data export features simplify moving data to reports or incorporating chemisorption data with data from other analytical techniques.

ChemiSoft TPx software can be set up to run independently of the instrument. This means that data files can be reviewed, calculation parameters changed, and reports generated on any computer anywhere, anytime.

Other functions of ChemiSoft

The AccuPyc II 1345 Series Pycnometers are fast, fully automatic pycnometers that provide high-speed, high-precision volume measurements and true density calculations on a wide variety of powders, solids, and slurries. After analyses are started with a few keystrokes, data are collected, calculations are performed, and results displayed. A minimal amount of operator attention is required.

Principle of Operation

This technique uses the gas displacement method to measure volume accurately. Inert gases, such as helium or nitrogen, are used as the displacement medium. The sample is sealed in the instrument compartment of known volume,the appropriate inert gas is admitted, and then expanded into another precision internal volume.

Total Density

On an elementary level, the volume of a solid material can be calculated by measuring its length, width, and thickness. However, many materials have within their structure surface irregularities, small fractures, fissures, and pores.

The GeoPyc automatically determines the volume and density of a solid object by displacement of Dry Flo, a solid medium. The medium is a narrow distribution of small, rigid spheres that have a high degree of flow ability and achieve close packing around the object under investigation. The particles are sufficiently small that during consolidation they conform closely to the surface of the object, yet do not invade pore space.

Repeatability and reproducibility are achieved by a controlled method of compaction. The sample cell in which the dry medium is placed is a precision cylinder. A plunger compresses the powder as the cell vibrates; the force of compression is selectable and, therefore repeatable from test to test. A preliminary compaction with only the displacement medium in the cell establishes a zero-volume baseline.

Reporting Functions

The GeoPyc has multiple operational modes that are accessed through the instruments smart touch screen. Operating modes including full blank, computed blank, and reference solid calibration with variance, which allows you to optimize speed and accuracy for your specific application.

Total

On an elementary level, the volume of a solid material can be calculated by measuring its length, width, and thickness. However, many materials have within their structure surface irregularities, small fractures, fissures, and pores.

Some of these voids or pores are open to the surface or closed within the structure of the solid material. Therefore, differences in the material volume depend on the measurement technique, measurement method, and the conditions under which the measurements were performed.

Operational Features

The GeoPyc is operated from an intelligent touch screen. Data acquisition and reporting are fully automated for convenient incorporation in LIMS or other data concentrating systems.

T.A.P Density Option

The GeoPyc T.A.P. density option obtains precise results comparable to conventional tap density analyzers, only it does it faster, quieter, and with a higher degree of reproducibility.

When equipped with the T.A.P. Density option, the GeoPyc measures the packing volume and calculates the bulk density of granular and powdered samples, including pharmaceutical and electrochemical materials, under a wide range of compaction conditions.

GeoPyc Envelope Density Analyzer

AccuPyc/GeoPyc Porosity Bundle Bundle

The ICCS incorporates:

To enable:

Key Features and Benefits:

Common Applications:

Common tests performed:

What is Air-permeability Particle Sizing?

The air-permeability technique is well established for measurement of the Specific Surface Area (SSA) of a sample powder. The SSA measured by this technique has been found to be a useful parameter in various industries such as pharmaceutical, metal coatings, paints, and even geological samples.

The MIC SAS II utilizes dual pressure transducers to measure pressure drop across a packed bed of powder. By varying the sample height and porosity while controlling the flow rate of air through the sample, the SSA and average particle size can be determined using the Kozeny-Carman equation.

Features and Benefits

Direct Comparison of SAS and FSSS

SentinelPro Unique Design Benefits

Shape Model Descriptions

Circle Models :

• Equivalent circular area diameter
• Equivalent circular perimeter diameter
• Bounding circle diameter
• Mean radius diameter
• Circularity
• Smoothness
• Compactness

Rectangle Models:

• Bounding rectangle length, width
• Bounding rectangle aspect ratio
• Rectangularity

Fiber Models:

• Fiber length, width
• Fiber aspect ratio
• Fiber curl

Ellipse Models:

• Equivalent elliptical area, width, length
• Bounding ellipse width, length
• Elliptical aspect ratio
• Ellipticity

Polygon Models:

• Polygon order
• Interior angle
• Convexity

Irregular Models:

• Feret length, width
• Feret aspect ratio
• Surface uniformity

Two Models Available

SentinelPro Features:

SentinelPro Instrument Features

SentinelPro Software Features

This process is repeated at given pressure intervals until the maximum preselected pressure is reached. Then the pressure can be decreased to provide a desorption isotherm. Each of the resulting equilibrium points [volume adsorbed and equilibrium pressure] is plotted to provide an isotherm.

HPVA II Benefits

Specification

Physical

• Height 88.9 cm (35 in.)
• Width 50.8 cm (20 in.)
• Depth 50.8 cm (20 in.)
• Weight 27.2 kg (60 lbs.)

Electrical

• Voltage 100 – 240 VAC.
• Frequency 50 – 60 Hz.

SSSpinTester Features

For Formulators, Important Improvements in Analyzing Precious Powders

SSSpinTester Specifications

Physical:

• Length: 18in.
• Width: 16in.
• Height: 15in. (includes the feet)
• Mass: ~22.5Kg or ~50lbs

Sample Volume:

Requires 0.5cc per test

Consolidation Pressure Range:

0.05 kPa to 72 kPa

Electrical:

• Voltage: 85 – 264 VAC
• Frequency: 50/60 Hz –
• Single Phase 9A

Typical Applications

Powdered Metals

Obtaining strength values at low consolidation pressures allows prediction of optimal powdered metal behavior. The SSSpinTester can measure the strength of heavy metal powder at actual fill pressure values for direct correlation to processing conditions

Additives (for energy)

Additives are typically introduced to coal combustion streams through pneumatic conveying. Measuring the strength of these powders at low to moderate compaction pressures can help with conveying this material.

Ceramics

Density variations of sintered ceramic powder can cause significant problems with dimensional tolerances of the final parts. Filling pressures are very low and the density variations depend on the strength of the material. Segregation can be prevented by the cohesive properties of the bulk

Pharmaceutical

Strength testing during formulation of pharmaceutical API powders is possible when only a very small quantity of the material is available. The weight variance from tablet to tablet is directly related to how the die fills. The filling depends on the strength of the material at low pressures

Food(fine powders only)

Food engineers need a quick test to measure the cohesion properties (strength and density) to determine if a particular mix will cause flow problems in the unit operation being used at the food plant. The SSSpinTester offers a fast and accurate measure of material strength at a full range of consolidation pressures.

Chemical

Often an engineer wants a quick test to measure the cohesion properties (strength and density) of a particular formulation. The optimal powder is one that has enough cohesion to prevent segregation, but not enough to cause density variations

Catalysts

Measuring the strength of catalyst material at low consolidation pressures can allow the scientist to determine if a catalyst will channel and correlate this information to the life of the catalyst in a fluid bed. The SSSpinTester measures the cohesiveness (strength and density) of the catalyst powder at actual process operating condition