Advances in Powder Metallurgy production technologies are generating an increased demand for tailored and tightly controlled powders with distinctive properties. The control of particle size distribution, as well as particle shape, is an important step in the quality control process. In this article we compare the three most commonly used methods for powder characterisation and highlights the pros and cons of each process.
Different measuring techniques provide different results – but what is the truth? The most common methods to determine the particle size are dynamic digital image analysis (DIA), static laser light scattering (SLS, also called laser diffraction) and sieve analysis. This article presents the advantages and drawbacks of each technique, their comparability among each other as well as detailed application examples.
Quality control is an essential part of the sugar production process as manufacturers must ensure that the product complies with the customers’ specifications. Not only the look, texture and taste of the final product depends on the size distribution, but also the solubility, tendency to aggregate, agglomerate and other properties which are important for industrial processes using sugar as a raw material. Hence, care must be taken that particles are neither too small nor too big. Traditionally, the particle size determination is carried out by sieve analysis which is a rather slow, labour-intensive method and commonly subject to measurement errors such as: too much sample material, worn out (uncalibrated) sieves, wrong sieve parameters (amplitude and sieving time) or simple calculation errors. An excellent alternative for the quality control of sugar is Retsch Technology’s CAMSIZER®. CAMSIZER® measurements are fast, automated, accurate and 100% comparable with sieve analysis. With these advantages the instrument can reliably replace sieving.
Catalysts are widely used as an important auxiliary material in the pharmaceutical and chemical industry. They are able to accelerate chemical reactions by lowering the activation energy, i.e. they change reaction kinetics. Thus, using catalysts in industrial processes has the advantage of higher productivity combined with less energy consumption.
In many processes a mixture of liquid or gaseous raw materials (e.g. petroleum) is transformed in a reactor with solid catalyst material. Depending on the desired reaction, catalysts of different materials such as ceramics, alumina, metal or alloys are used. To save costs, inexpensive substrates can be coated with the actual catalyst (e.g. platinum or rhodium).
The active surface as well as the form of the catalysts is crucial for their efficiency. It is important that sufficient free volume is available for the reactants. Moreover, the counter pressure built up by the catalyst must not be too high. Spherical, comb-shaped or rod-shaped geometries have proven to be especially suitable. The rod-shaped catalysts have different shapes; their profiles can have an ellipsoid, trilobe or quadrulobe shape.
With an estimated 1.4 billion cups of coffee consumed worldwide every day, there is a great and ever increasing demand for coffee beans in the global market. The taste of coffee is influenced by the roasting of the beans, their grinding degree and the method and quality of the preparation. Different types of preparation by brewing and filtering (e.g. espresso machine, filter coffee or mocca) require different grinding degrees of the coffee powder to obtain an aromatic result. When roasted beans are ground to powder, the determination of the particle size is a critical aspect because the particle size influences the brewing and filtering properties and thus the taste and salubriousness of the coffee.
Particle size analysis is an important step in the quality control of many industrial production processes. This article describes the implementation of Dynamic Image Analysis (DIA) in the fertilizer industry as a typical example. DIA is used in the same way in other industries, for example for pharmaceuticals, foodstuff, plastics, chemicals, metal powders and even granulated explosives.
Sieve analysis and laser diffraction are long established methods for the determination of particle size distributions. Dynamic Image Analysis (DIA) is another particle analysis technology to measure particles > 1 micron which has numerous advantages over these methods.
Retsch Technology’s particle analyzers CAMSIZER and CAMSIZER XT, which are based on DIA technology, evaluate images of the particles which provide considerably more information on the particles than, for example, a light scattering pattern produced by a laser diffraction particle analyzer. These only allow for an indirect measurement of the particle size. The determination of parameters such as the length, width, or sphericity of particles is only possible by using image analysis.
Traditionally, particle size distribution analysis of pharmaceutical powders and granules is carried out by sieve analysis, microscopy or with laser diffraction. These methods are established in the pharmacopoeia and used routinely in pharmaceutical laboratories all over the world. With the introduction of Dynamic Image Analysis (DIA) as an alternative method, it is now possible to measure particle sizes >1 micron of powders, granules, pellets and suspensions as well as particle shape. A number of trials clearly demonstrate the advantages of DIA compared to the established particle sizing methods.
The CAMSIZER XT has been successfully installed at building material plants around the world replacing sieve analysis by providing quick, reliable high resolution results while still matching historic sieve data. The typical measurement time varies between 1 to 3 min depending on the desired measuring statistics. Reported result parameters include smallest diameter, length, mean diameter, aspect ratio, symmetry, sphericity, and convexity.
Quality control of solder powders with the CAMSIZER XT - solder pastes are used in the electronics industry for reflow-soldering of SMD (surface mounted devices) components on printed circuit board (PCB) assemblies. The solder paste is printed on the contact pads and the components are mounted on these pads. The paste attaches the components on the PCB until the PCB is heated in an oven where the solder paste melts. The melt connects the electronic components (resistors, transistors, ICs, EPROMS, etc.) and the contact pads of the PCB providing the electric contact and mechanical fixture after cooling and solidification. An essential component of solder paste, beside the flux, is the solder powder.
Sieve analysis according to ICUMSA Method GS2/9-37 is the standard for particle sizing of crystal sugar. Officially, all labs follow these guidelines, and comparable results should be seen in round robin tests. On a closer look however, each lab follows procedures that deviate slightly from those outlined in the ICUMSA Method. As a result, the size distributions measured by different labs vary remarkably. In this article we will discuss the typical deviations that can be found in the daily operation, and propose a new analysis method which provides more reproducible and reliable results.
Laser diffraction is the most frequently used measurement technique for the analysis of particle size distributions in the range 1 micron to 1 mm in the context of quality control. Modern laser diffraction systems offer some convincing advantages such as short measurement times, easy operation and reproducible analysis results. However, they also have various disadvantages: Even if the instruments have been calibrated and validated, an absolute particle size measurement is not possible. Various round robin tests have shown that the analysis results depend strongly on the type of instrument and even on the particular model and software version.
The quality control of fine powders can be substantially improved with the new CAMSIZER XT: More precise and faster analysis of particle size and particle shape helps to improve the product quality, reduce rejects and save costs.