White Paper: Ultrafine Grinding with Laboratory Ball Mills
How are nano particles produced? The “Bottom-Up” method synthesizes particles from atoms or molecules. The “Top-Down” method involves reducing the size of larger particles to nanoscale, for example with laboratory mills. Due to their significantly enlarged surface in relation to the volume, small particles are drawn to each other by their electrostatic charges. Nano particles are produced by colloidal grinding which involves dispersion of the particles in liquid to neutralize the surface charges. Both water and alcohol can be used as dispersion medium, depending on the sample material. Factors such as energy input and size reduction principle make ball mills the best choice for the production of nanoparticles.
White Paper Sieve Analysis - Different methods for a variety of applications
The determination and knowledge of the particle size distribution is an essential part of the quality control process for industrial products. From incoming and production control to research and development sieve analyses are used to determine a number of parameters or simply the particle size. Easy handling, low investment cost and high accuracy make sieve analysis one of the most frequently used procedures for measuring the particle size. This white paper gives an overview of the different sieving techniques and describes the necessary steps to ensure reliable results.
Anche se la macinazione viene svolta in condizioni ideali, gli stress meccanici che il campione esercita sulla superficie degli strumenti di macinazione può causare abrasione. Tuttavia, selezionando un mulino e degli accessori adatti è possibile minimizzare questo effetto. Se il campione deve essere macinato a pezzature inferiori ai 100 microns, le forti forze meccaniche richieste aumentano l’abrasione.
Los más precisos resultados de trituración en el más breve tiempo se consiguen con los nuevos molinos planetarios de bolas, de Retsch. Con el PM100 y el PM200, Retsch presenta una nueva generación de molinos planetarios de bolas con uno o dos unidades de trituración, que establecen nuevos estándares de rendimiento en este segmento de la producción.
El nuevo molino ultracentrífugo ZM 200 de RETSCH es un molino de rotor no sólo extremadamente rápido y cuidadoso con el material molido, sino también de uso universal gracias a su amplia gama de accesorios.
El agotamiento de los recursos y el aumento del precio de los combustibles primarios tales como el petróleo, el gas o el carbón han obligado a la industria del cemento a buscar fuentes alternativas de energía. Otro factor contribuyente es, sin duda, el comercio de emisiones que hace todavía más rentable el cambio a fuentes de energía con un balance neutro de CO2, en su mayoría combustibles no fósiles. En los últimos años, se ha registrado un incremento en el uso de fuentes de energía alternativas, especialmente por aquellas industrias con una alta demanda energética. En consecuencia, viene ganando cada vez más importancia el empleo de combustibles secundarios o alternativos, que en su mayoría son extraídos de residuos urbanos e industriales – es decir, residuos urbanos que no han podido ser recuperados ni reciclados.
Nanoteilchen, d.h. Partikel mit einem Durchmesser von weniger als 100 Nanometer, werden seit vielen Jahren von Wissenschaftlern erforscht. Zum einen lassen sie sich im „Bottom-up“ Verfahren aus Atomen oder Molekülen synthetisieren. Im “Top-Down“ Verfahren hingegen werden größere Partikel, z.B. mit Hilfe von Labormühlen, zerkleinert. Kleine Partikel weisen durch das extrem vergrößerte Verhältnis von Oberfläche zu Volumen erhöhte Oberflächenladungen auf, so dass die Partikel elektrostatisch zueinander gezogen werden. Daher können Nanopartikel nur durch Nassvermahlung (Kolloidvermahlung) erzeugt werden.
Particle size analysis and particle size distribution are important criteria for the quality control of bulk materials. In a running production process, the results of a quality check must be available quickly to allow for immediate adjustment of the production parameters. Depending on the expected particle size and sample volume, different sieving methods and sieving machines are suitable for analysis. The method used for particle size analysis is primarily determined by the fineness of the material to be sieved. For dry sieving of samples with particle sizes below 40 microns, air jet sieving is the method of choice.
The Emax is an entirely new type of ball mill which was specifically designed by RETSCH for high energy milling. The impressive speed of 2,000 min-1, so far unrivaled in a ball mill, in combination with the special grinding jar design generates a vast amount of size reduction energy. The unique combination of impact, friction and circulating grinding jar movement results in ultrafine particle sizes in the shortest amount of time. Thanks to the new liquid cooling system, excess thermal energy is quickly discharged preventing both sample and mill from overheating, even after long grinding times.
The overall procedure of X-ray fluorescence analysis may be divided into three different stages: sampling, sample preparation and the actual spectrometric analysis itself. Of these three, it is usually the mechanical sample preparation that takes up most of the time and will therefore be discussed in this application report.
Quality control is an important aspect of cement production. Sample preparation is an essential part of it, because only a representative and reproducible processing of the sample material ensures reliable and meaningful analysis results. RETSCH offers a range of instruments for dividing, crushing, grinding and sizing all materials which are involved in the production process of cement, including secondary fuels. To ensure the right choice of instrument for the right sample material, Retsch offers free-of-charge sample testing in application laboratories all over the world.
The following situation is typical for many production plants: After a routine quality check, the production process is stopped or an already produced batch is suspended, because the analysis results were not within the relevant critical values. But does the tested product really deviate from the specifications? The quality control managers are convinced of this because modern analysis instruments provide results with very low tolerances. The sample in question was tested several times and the result was confirmed. The question is why the product does not match the specifications although the production parameters have not been changed in any way. The possibility that the tested product is indeed deficient cannot be excluded. However, it is often not the product itself which causes irregular analysis results but a lack of understanding of the steps which come before the analysis.
Representative sampling of large sample volumes is an integral part of the physical and chemical analysis of bulk goods and has a decisive influence on the quality of the results. Extraction of a sample from the bulk is not always carried out in a way to ensure representativeness. This is a widespread flaw in the quality control process with a negative impact on the subsequent analysis results. Therefore, more attention should be paid to the correct sampling procedure. Sample division is often considered as a labor-intensive process which not always leads to representative results. RETSCH provides some convenient solutions which help to improve working conditions and thereby the quality of the sampling process.
The XRD-Mill McCrone preserves the crystal lattice structure of the sample -
With resources becoming increasingly scarce, innovative technologies allowing for sustainable use of raw materials are much sought after. The mineralogist Dr. Robert Moeckel is researching mineral and metallic raw materials at the Helmholtz-Institute for Technology of Resources in Freiburg, Germany. Dr. Moeckel´s research projects involve pulverization and homogenization of mineral samples prior to x-ray diffraction (XRD) analysis.
With ever increasing socio-economic and geo-political demands, the use of secondary fuels in cement manufacture is a well-established practice for reducing both costs and CO2 emissions. The depletion of resources, combined with an increasing demand for primary fuels such as oil, gas or coal, make it paramount for energy consuming industries to search for alternative energy sources.
Particle analysis of large quantities of bulk goods is usually done by vibratory sieving. In most vibratory sieve shakers in the market the sieve stack is mounted on springs which oscillate vertically. However, to evenly distribute the material over the entire sieve surface, the so called 3D vibratory sieving as it is used in the AS 450 control is the most suitable method. This is characterized by a circular motion superimposing the vertical throwing motion so that the sample material is moved over the whole sieve.
Air jet sieving is usually the method of choice for dry sieving of materials with particle sizes below 40 microns. However, it is also a faster alternative to vibratory sieving of materials of up to 250 microns.
The Cologne Cathedral is a venerable old building whose historic substance is preserved by continuing restoration works. Mortar is one of the construction materials that the conservators use for preservation and restoration of the ancient stones. To obtain mortar with optimum quality, the conservators at the cathedral workshop in Cologne use a RETSCH sieve shaker to determine the particle size distribution of the material.
A faultless and comparable analysis is closely linked to an accurate sample handling. Only a sample representative of the initial material can provide meaningful analysis results. Rotating dividers and rotary tube dividers are an important means to ensure the representativeness of a sample and thus the reproducibility of the analysis. Correct sample handling consequently minimizes the probability of a production stop due to incorrect analysis results. Thus correct sample handling is the key to effective quality control.