NATURAL ZEOLITES IN AIR DRYING

The local clinoptilolite from Bigadis region in Turkiye, was used for air drying in packed column. The effective diffusion coefficient of water in natural zeolite was found as 5×10^-10 m² s^-1 from isothermal uptake measurements. Effects of packing height and airvelocity on breakthrough curves were studied.     

Modeling of ferrofluid magnetic actuation with dynamic magnetic fields in small channels

One of the most important and promising research areas in biomedical and micropumping applications is magnetic actuation of ferrofluids with dynamic magnetic fields. For ensuring the use of ferrofluids in various applications in engineering fields, their flows generated by magnetic fields should be extensively investigated and simulated. In this study, simulations of ferrofluid actuation with dynamic magnetic fields were performed by modeling it using the COMSOL Multiphysics software, and iron oxide nanoparticle-based ferrofluids at different angles of rotating magnets were considered to provide insight into ferrofluid flow in small channels. Ferrofluid flows were modeled at different magnetic flux densities provided by rotating magnets, and velocity profiles inside the channel were analyzed. It was shown that ferrofluid actuation can be considered as a futuristic micropumping alternative, simulation results matched well with the experimental results of previous work, and the established model could serve as a tool to analyze ferrofluid flows generated by dynamic magnetic fields. The results of the model show that flow rates up to 100 µl/s can be reached at a rotation angle of 30° by using dynamic magnetic fields. Various applications including biomedical applications might be envisaged.     

On a passivity of the Arnoldi based model order reduction forfull-wave electromagnetic modeling

Progress in MEMS and packaging design has made significant changes in the requirements for modeling tools. In order to design a modern microdevice or interconnect system it is no longer sufficient to limit the analysis to quasielectrostatic modeling due to smaller size and higher operation frequencies of the microdevices. On the other hand, a “full-wave” analysis produces huge systems of equations which require tremendous amounts of computational resources. Many model order reduction algorithms were developed in order to solve this problem. But the passivity of the reduced system is still an issue for “full-wave” models. This paper will describe the Arnoldi based model order reduction algorithm for “full-wave” electromagnetic analysis and will show that this algorithm preserves passivity of the reduced system     

Time resolved determination of electrical field distributions within dynamically biased power devices by spectral EBIC investigations

Time resolved investigations of electric field distributions in the near-surface regions of a dynamically biased power device using spectral EBIC microscopy are introduced. The technique described provides a facility for determination of local electrical field strengths inside devices by factoring out induced currents in their spectral components. A developed setup enhances the signal to noise ratio and reduces disturbing signals up to 160 dB, offering consequently a possibility for EBIC analysis at high switching currents of the DUT. Quantitative E-field distributions at steady state device biasing conditions and variations of the field during reverse and forward recoveries are shown under operating conditions for the example of a power diode with a guard ring as a field termination structure.     

The synthesis and characterization of Cu(II) phthalocyanine bearing peripheral monoazacrown ethers and a spectral investigation of its film forming character

The synthesis, liquid crystalline behavior and self-organizing properties of Cu(II)Pc bearing monoazacrown ether moieties that contain long alkyloxyphenyl N-pivotal groups are described. The Cu(II) phthalocyanine derivative has a hexagonal, columnar structure; optical absorption and vibrational spectroscopy revealed a predominantly co-facial interaction between the chromophores and their orientation parallel to a NaCl surface. It is proposed that such homeotropic alignment is attributable to the ability of the pendant monoazacrown ether groups to coordinate the Na⁺ ions within the NaCl surface.     

Nanoscale thermally induced stress analysis by complementary Scanning Thermal Microscopy techniques

Thermally induced stress is determined using boundary values obtained by complementary Scanning Joule Expansion Microscopy and Scanning Thermal Microscopy. The stress function is then solved with the Finite Element Method. Surface stress analysis as well as stress analysis of multilayered structures are performed in order to demonstrate the application of the developed measurement technique to reliability investigations.     

Front- and backside investigations of thermal and electronic properties of semiconducting devices

Shrinking feature sizes of electronic devices are leading to an increase of the internal electrical fields resulting in an increased hot electron generation. Consequently, the investigation of the resulting electrical device degradation and breakdown mechanisms gain in significance. A powerful tool for these investigations is the photon emission microscope (PEM). A disadvantage of this technique, however, is the inability to image radiative recombination processes which are taking place underneath metallization layers. In this paper, we will show that PEM investigations from the backside overcome problems of failure localization caused by opaque metal contacts. A further scope of this work is to compare the information which is obtained by collecting the emitted light with thermal properties like failure induced hot spots inside a device. This thermal characterization is carried out with a scanning thermal microscope (SThM), which is used for the localization of failures in integrated devices and for backside measurements on thinned substrates.     

Semiquantitative method for the evaluation of grease barrier coatings

Many tests are known for testing the grease barrier performance of coatings in paper or paperboard. Some are manifested in standard procedures such as TAPPI, ASTM, or ISO, but as many procedures were developed and modified by companies and research groups. Mainly the test methods are based on visually detecting the amount of oil, which is in most cases dyed for better contrast, penetrating through the coating, meaning the procedures are based on a subjective visual evaluation and thus often not linked for instance to a statistical meaningful physical value. We found that by using a slightly modified ASTM D 722 test the L*a*b* color coordinates determined with a commercial handheld spectrophotometer are related to the grease barrier performance of an organic coating. By applying this new method the penetration time of an oil/dye mixture could be correlated to the lightness L* and chromaticity b* and fitted by an exponential function. Furthermore, the coating was slightly modified and an improvement or worsening of the grease barrier could be detected clearly outside of the statistical scatter of a control series. We call this method semiquantitative, since the level of grease barrier of a coating is not measured directly by a quantitative value, but color coordinates are correlated in a series to the effectiveness of the grease barrier.