I semiconduttori sono utilizzati per una grande varietà di applicazioni elettroniche, come circuiti integrati (microprocessori, microcontrollori, ecc.) rilevatori ottici e sorgenti di radiazioni (es. emettitori di luce), ma in modo particolare per i fotovoltaici, tramite i quali l’energia solare viene trasformata in potenza elettrica. Per la maggior parte delle applicazioni, il silicio è il materiale semiconduttore scelto.
I mulini a taglienti vengono utilizzati in diverse aree della preparazione dl campione alle analisi successive. Tipiche applicazioni includono la riduzione di combustibili da rifiuto, la macinazione di campioni di biomasse per ricerche nell’ambito delle energie rinnovabili, il controllo dei prodotti nell’abito delle normative RoHS and WEEE, o nel recupero dei materiali preziosi – la varietà di campione è notevole.
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.
Planeten-Kugelmühlen haben seit jeher einen festen Platz in der täglichen Laborpraxis zur Feinzerkleinerung unterschiedlichster Materialien. Neben dem Mischen und Zerkleinern hat sich in den letzten Jahren auch im mechanischen Legieren z.B. thermoelektrischer oder hochkoerzitiver Materialien ein weiteres Anwendungsgebiet ergeben.
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.
Modern analytical methods increase precision and push detection limits to make even the smallest traces of sample components detectable. Despite this development sample preparation, which is carried out prior to the actual analysis, is frequently neglected. Errors caused by lacking accuracy in sample preparation have a much bigger impact than errors made during analysis. Just like an iceberg which is mostly hidden under water, only a small part of the sum of errors is perceived whereas the major part of potential errors is not taken into account (fig. 1). One of the reasons may be the fact that sampling and sample preparation have always been done in a traditional way which has become a routine over the years and is no longer considered as having a critical influence on the subsequent analyses.
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.
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.
Some sample materials have properties which make size reduction at ambient temperature impossible. If, for example, very elastic materials need to be ground or volatile components have to be preserved for further analysis, it is essential to carry out cryogenic grinding. The use of liquid nitrogen helps to embrittle the sample, thus improving its breaking properties, and preventing volatile substances from escaping due to the frictional heat produced by the grinding process.
The EU directive 2000/53/EG stipulates that as of 2015 95 % of the weight of a car that has reached the end of its life span have to be recycled. The work of ARN is strongly focused on this objective. Together with partner companies they make sure that old cars are processed in an environmentally compliant way. The recycling chain begins with the companies that dismantle the car and remove raw materials and liquids. Waste management companies collect these materials and deliver them to the processing companies who reuse the materials in accordance with high production standards.
The SM 300 excels especially in the tough jobs where other cutting mills fail. It has a freely selectable speed range from 700 to 3,000 rpm with high torque. The mill is convenient to operate and easy to clean. Reliable and extremely efficient sample preparation in the laboratory is now guaranteed with the SM 300.
Preparing electronic waste for obtaining representative analytical samples. A solution for converting an electrical appliance into a meaningful analytical sample is described using a remote-controlled toy car as an example.
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.
Grinding samples with volatile components - Cottbus University, Germany