Manufacturing Techniques for Metals - Fabrication of Microreactors Made from Metals and Ceramic - Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)

Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)

2. Fabrication of Microreactors Made from Metals and Ceramic

Juergen J. Brandner

The material used to manufacture microstructure devices heavily depends on the desired application. The temperature and pressure ranges of the application, the corrosivity of the used fluids, the need to avoid catalytic blind activities or to integrate catalytically active materials, thermal conductivity and temperature distribution, specific heat capacity, electrical properties, and some other parameters have a large influence on the choice of material. Last but not least, the design and dimensions of the microstructures need to be considered. Very specific designs are achieved only with special materials because a specific manufacturing technique is needed. It might also be necessary to obtain a special surface quality, which is achievable only with a specific manufacturing technique and material.

Moreover, depending on the number of devices needed, some manufacturing techniques are well suitable, while others are not.

In this chapter, the fabrication of microstructure components and devices out of metals and ceramic will be described briefly as well as bonding, sealing, and packaging of devices. Manufacturing processes for metal microstructure components and ceramic microstructures are described, focusing on some well-established technologies. The technologies are not described in detail. Detailed information can be found in Refs [1–7] or all the other references provided. A very short bonding section, in which the most common bonding and sealing techniques are briefly described, completes the description for metals and ceramic [4, 8].

Two different principal manufacturing technologies can be used with the discussed materials, for example, erosive and generative manufacturing. Following this, technologies such as embossing, roll forming, or molding are considered to be included into the generative techniques.

2.1. Manufacturing Techniques for Metals

Metals and metal alloys are the most often used materials for conventional devices in process engineering as well as in microprocess technology. The materials used range from noble metals such as silver, rhodium, platinum, or palladium via stainless steel to copper-, titanium-, aluminum-, or nickel-based alloys [1, 4–7]. Most manufacturing technologies for metallic microstructures have their roots either in semiconductor (which means in most cases silicon) device production or in conventional precision machining, which is linked to fine mechanics or clock and jewelry making. The processes well known from these techniques have been used for microstructure dimensions. Then, they have been adapted and improved to reach the desired precision and surface quality. In some rare cases, it was possible to use the same manufacturing process for macroscale and microscale devices and to reach sufficient results. In most cases, more or less strong changes within the design of the device, the methodology of the process, and the manufacturing process itself were necessary to provide the accuracy and quality needed for microstructure devices suitable for process engineering. Almost all but two techniques used for microstructures in metal are abrasive; the exception (selective laser melting, SLM) will be discussed later.