@article{63720,
  abstract     = {{The aging behavior of closed-cell polyurethane (PUR) foam, a material widely used in household refrigeration, is studied by examining the variation of cell gas composition and thermal conductivity over time. Aging is primarily driven by gas permeation, wherein the initially present cell gases carbon dioxide and cyclopentane are progressively replaced by nitrogen and oxygen from the ambient, resulting in an increased thermal conductivity and reduced insulation performance. The cell gas composition is measured over 1400 days employing gas chromatography, and the thermal conductivity of the foam is measured over 190 days. Morphological foam characteristics, such as average cell diameter, are determined via scanning electron microscopy and barrier measurements are performed to estimate the effective diffusion coefficient of oxygen. To simulate the aging process, one-dimensional and three-dimensional models are developed for both diffusive mass transfer as well as heat transfer. The present model for the thermal conductivity explicitly accounts for condensation effects, i.e. partial condensation of cyclopentane and carbon dioxide occurring at around 12°C, which significantly influences the insulation behavior of the foam. Sensitivity analyses indicate that an initial cell gas pressure of approximately 0.7 bar yields results that closely coincide with the experimental measurements, where the three-dimensional model demonstrates better accuracy. These measurements and simulations provide valuable insights for evaluating and predicting the long-term degradation of the insulation performance of PUR foams.}},
  author       = {{Schumacher, Daniel and Guevara-Carrion, Gabriela and Kasper, Tina and Paul, Andreas and Elsner, Andreas and Peters, Bettina and Wollny, Wenke and Bluemel, Marcus and Hoelscher, Heike and Brzoska-Steinhaus, Nicola and Heil, Klaus and Schleelein, Lukas and Becker, Wolfgang and Gries, Ulrich and Vrabec, Jadran}},
  issn         = {{1359-4311}},
  journal      = {{Applied Thermal Engineering}},
  keywords     = {{Polyurethane, Foam, Gas permeation, Diffusion models, Thermal conductivity, Condensation, Gas chromatography, Scanning electron microscopy}},
  publisher    = {{Elsevier BV}},
  title        = {{{Aging of polyurethane foam: Experimental analysis and modeling of cell gas composition and thermal conductivity}}},
  doi          = {{10.1016/j.applthermaleng.2026.129850}},
  volume       = {{289}},
  year         = {{2026}},
}

@article{43441,
  abstract     = {{This paper reveals the 3D character of the intermetallic layer at the aluminum–steel interface which pops
up above the original sample surface during annealing. Popping out of the intermetallics was proven using
atomic force microscopy. The phase expands out of the plane due to the exothermic formation of the Al5Fe2
phase and the feasibility of surface diffusion. Milling by a focused ion beam enabled the comparison of the
chemical composition of the surface layer with the bulk interface, showing no difference. The growth direction
is both towards aluminum and steel — the main diffusion flux is from aluminum towards steel, and the new
intermetallic phase emerges at the steel side. The shortage of Al atoms causes a shift of the intermetallic as a
whole towards aluminum.}},
  author       = {{Šlapáková, Michaela and Kihoulou, Barbora and Veselý, Jozef and Minárik, Peter and Fekete, Klaudia and Knapek, Michal and Králík, Rostislav and Grydin, Olexandr and Stolbchenko, Mykhailo and Schaper, Mirko}},
  issn         = {{0042-207X}},
  journal      = {{Vacuum}},
  keywords     = {{Al-steel clad, twin-roll casting, 3D characterization, atomic force microscopy, diffusion direction, surface growth}},
  publisher    = {{Elsevier BV}},
  title        = {{{3D-structure of intermetallic interface layer in Al–steel clad material}}},
  doi          = {{10.1016/j.vacuum.2023.112043}},
  volume       = {{212}},
  year         = {{2023}},
}

@article{9899,
  abstract     = {{Bainite is a steel microstructure consisting of three phases, bainitic ferrite, austenite and carbides. It forms in two different morphologies, upper and lower bainite, where different diffusion mechanisms are dominant. The aim of this work is to simulate both transformations within a unified model. To this end, we extend an own previously published model for lower bainite with diffusion across the phase interface. As a central idea we introduce weighted Helmholtz energy functions and a weighted mobility tensor, respectively. The individual Helmholtz energy functions and mobility terms are related to the different diffusion mechanisms which are responsible for the formation of both morphologies. Two representative examples illustrate the capability of the coupled phase field/diffusion model and show the expected behaviour.}},
  author       = {{Düsing, M. and Mahnken, R.}},
  issn         = {{0020-7683}},
  journal      = {{International Journal of Solids and Structures}},
  keywords     = {{Coupled phase field/diffusion model, Bainite, Multiphase field method, Cahn–Hilliard diffusion, Diffusion across the interface, Lower bainitic transformation, Upper bainitic transformation, Thermodynamic framework, Microforce balance}},
  pages        = {{172--183}},
  publisher    = {{Elsevier}},
  title        = {{{„A coupled phase field/diffusion model for upper and lower bainitic transformation”}}},
  volume       = {{135}},
  year         = {{2018}},
}

@inproceedings{9868,
  abstract     = {{In order to increase mechanical strength, heat dissipation and ampacity and to decrease failure through fatigue fracture, wedge copper wire bonding is being introduced as a standard interconnection method for mass production. To achieve the same process stability when using copper wire instead of aluminum wire a profound understanding of the bonding process is needed. Due to the higher hardness of copper compared to aluminum wire it is more difficult to approach the surfaces of wire and substrate to a level where van der Waals forces are able to arise between atoms. Also, enough friction energy referred to the total contact area has to be generated to activate the surfaces. Therefore, a friction model is used to simulate the joining process. This model calculates the resulting energy of partial areas in the contact surface and provides information about the adhesion process of each area. The focus here is on the arising of micro joints in the contact area depending on the location in the contact and time. To validate the model, different touchdown forces are used to vary the initial contact areas of wire and substrate. Additionally, a piezoelectric tri-axial force sensor is built up to identify the known phases of pre-deforming, cleaning, adhering and diffusing for the real bonding process to map with the model. Test substrates as DBC and copper plate are used to show the different formations of a wedge bond connection due to hardness and reaction propensity. The experiments were done by using 500 $\mu$m copper wire and a standard V-groove tool.}},
  author       = {{Althoff, Simon and Neuhaus, Jan and Hemsel, Tobias and Sextro, Walter}},
  booktitle    = {{Electronic Components and Technology Conference (ECTC), 2014 IEEE 64th}},
  keywords     = {{adhesion, circuit reliability, deformation, diffusion, fatigue cracks, friction, interconnections, lead bonding, van der Waals forces, Cu, adhering process, adhesion process, ampacity improvement, bond quality improvement, cleaning process, diffusing process, fatigue fracture failure, friction energy, friction model, heat dissipation, mechanical strength, piezoelectric triaxial force sensor, predeforming process, size 500 mum, total contact area, van der Waals forces, wedge copper wire bonding, Bonding, Copper, Finite element analysis, Force, Friction, Substrates, Wires}},
  pages        = {{1549--1555}},
  title        = {{{Improving the bond quality of copper wire bonds using a friction model approach}}},
  doi          = {{10.1109/ECTC.2014.6897500}},
  year         = {{2014}},
}