Micro powder-injection moulding of metals and ceramics

Development of micro-MIM/-CIM was started at Forschungszentram Karlsrahe with the aim of creating a process suitable for a wide range of materials as well as for medium-scale and large-scale production of micro components. Using enhanced machine technology and special tempering procedures, this process enables the manufacturing of metal and ceramic devices with smallest wall thicknesses of 50 Μm and structural details of less than 3 Μm. Using ultrafine ceramic powders (e.g. zirconia) and high-quality LIGA mould inserts, surface qualities ofR _a = 40 nm or R_max ≤ 3 mm could be obtained. Possible practical applications are demonstrated by components of micro-annular gear pumps made of zirconia for future handling of very small volumes of dangerous fluids and micro samples (tensile and bending specimens) suitable for mechanical testing of metals (316L, 17-4PH) and ceramic materials (A1₂O₃, ZrO₂) in the micrometre range.     

Investigation of the selective catalytic reduction of NO by NH3 on Fe-ZSM5 monolith catalysts

Photocatalytic nitric oxide (NO) decomposition and reduction reactions, using carbon monoxide (CO) as a reducing gas, have been investigated over Degussa P25 titanium dioxide photocatalysts, using a continuous flow reactor. The effects of thermal pretreatment temperature and reaction gas composition on the activity and selectivity of the decomposition and reduction reactions have been evaluated. Prepared materials were characterised by X-ray diffraction (XRD), N₂ physisorption, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) and findings from these techniques were used to explain the observed photocatalytic properties. XRD and TEM results indicated that for the pretreatment temperatures used (70, 120, 200, 450 and 600 °C) there was no appreciable change in the phase composition and the original composition of ca. 77 vol.% anatase and 23 vol.% rutile was maintained even after treatment at 600 °C. It was found that the photocatalytic activity for both the decomposition and reduction reactions decreased with increasing pretreatment temperature. This was attributed to the removal of surface hydroxyl species that act as active sites for reaction. For the decomposition reactions the only products observed were nitrogen and nitrous oxide and the selectivity for nitrogen formation remained constant (ca. 23%) regardless of the pretreatment temperature. The presence of CO in the reaction gas had a dramatic effect on the selectivity of the reactions with nitrogen selectivities as high as 65% being observed. It was found that as the CO/NO ratio increased the selectivity for nitrogen formation increased.     

New and efficient high-temperature processes with circulating fluid bed reactors

Starting with a brief review of the development of the circulating fluid bed (CFB) reactor principle, its main features as an important tool for efficient and thus environmentally acceptable processing of fine particulate solids, typically less than 150 μm diameter, are discussed. Various new industrial processes and high temperature process options starting with alumina calcination are described. Developing applications in the cement, metallurgical and chemical industries are approaching large-scale industrial importance. Efficient combustion or pressure gasification of fossil fuels and carbon-containing residues, fulfilling increasingly strict environmental legislation, is by far the most rapidly expanding field of application. In support of these developments our fundamental understanding of the fluid dynamics of CFB riser and of cyclone precipitation at high solid loadings has to be steadily improved. The reaction behaviour of aggregating fine particulate solids of varying size distributions also remains an open question.     

Messung der anisothermischen statischen Entfestigung eines mikrolegierten Stahls nach der Warmumformung

Beschreibung eines Auswerteverfahrens für die statische Entfestigung unter anisothermischen Bedingungen von mit Niob mikrolegiertem Baustahl. Umformung mit dem Flachstauchversuch. Doppelschlagtechnik. Variation von Abkühlgeschwindigkeit Umformtemperatur und Umformgrad. Erstellung eines anisothermischen Zeit-Temperatur-Entfestigungs-Schaubildes.     

Biocide polymers, 19. Modification of carboxyl groups containing resins with 3(5)-methylpyrazole

Polymeric inhibitors of nitrification have been prepared by reversible attachment of 3(5)-methylpyrazole to poly(acrylic acid-co-divinylbenzene) and poly(4-vinylbenzoic acid-co-divinylbenzene) containing 86 mol-% and 88 mol-% carboxyl groups, respectively. Pyrazolide bonds between the bioactive agent and crosslinked copolymers were formed by means of aminolysis of reactive derivatives of the resins containing mixed anhydride groups or acid chloride groups. The modified resins had pendantly bound 3(5)-methylpyrazole residues in the range of 7 to 36.4 wt.-% and were subjected to hydrolysis in order to study the influence of crosslinking on the release rate of the active ingredient. The results obtained were discussed.