Spark plasma sintering of B4C and B4C-TiB2 composites: Deformation and failure mechanisms under quasistatic and dynamic loading

Spark plasma sintering (SPS) was employed to consolidate powder specimens consisting of B₄C and various B₄C-TiB₂ compositions. SPS allowed for consolidation of pure B₄C, B₄C-13 vol.%TiB₂, and B₄C-23 vol.%TiB₂ composites achieving ≥99 % theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth due to long sintering times. Electron and x-ray microscopies determined homogeneous microstructures along with excellent distribution of TiB₂ phase in both small and larger-scaled composites. An optimized B₄C-23 vol.%TiB₂ composite with a targeted low density of ～3.0 g/cm³ exhibited 30–35 % increased hardness, fracture toughness, and flexural bend strength compared to several commercial armor-grade ceramics, with the flexural strength being strain rate insensitive under quasistatic and dynamic loading. Mechanistic studies determined that the improvements are a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B₄C matrix in compression and TiB₂ phase in tension, and c) TiB₂ phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB₂ serves as a toughening and strengthening phase, and scaling of SPS samples show promise for the manufacture of ceramic composites for body armor.     

Aktuelle Aktivitäten zu den europäischen Rohstoff-Initiativen

The European Initiatives manifested in the Communications of the European Commission on Raw Materials, in the Strategic Implementation Plan of the European Innovation Partnership on Raw Materials and in the 2014 Call of the European Institute for Innovation & Technology (EIT) for a Knowledge and Innovation Community (KIC) on Raw Materials lead to manifold Austrian activities on Government level and on level of the Montanuniversitaet Leoben. The ESEE Region, thus East- and Southeast Europe has a special role.     

Self-healing through microencapsulated agents for protective coatings

The use of microcapsules containing healing agents, which can serve as source of self-healing for coatings, was investigated. The appropriate self-repairing coatings are designed to be used for heavy-duty corrosion protection or for the protection of moisture-sensitive substrates like wood. Microcapsules based on thermoset resins (urea–formaldehyde and melamine–formaldehyde) which contained components of different chemical natures (resins or inhibitors) were fabricated using emulsion techniques. The subsequent characterization included optical, fluorescence, and electron microscopy as well as adapted microindentation techniques to determine capsule break forces. Different model coatings were formulated making use of varying amounts of healing agent-charged microcapsules. The coated samples were then injured under controlled conditions (by Erichsen cupping in the case of steel, by simulated hail in the case of wood) and then subjected to salt spray testing (natural and accelerated), weathering, or even real-life exposure, always in comparison with a blank. The results obtained demonstrate the superiority of microcapsule-based self-healing coatings compared to classical protection formulations, and appropriate coating systems have in the meantime been successfully brought to the market.     

Introduction to the special issue on IEEE NEWCAS 2017

A contactless detector is presented for evaluating hand tremors caused by exercise-induced fatigue and early Parkinson’s disease. The device consists of a spiral coil, a microcontroller, and an inductive sensor circuitry. Theory shows that the resonant frequency of the circuitry increases when the distance between the hand and the spiral coil decreases, thus small variations of distance from tremor can be detected from the changes of resonant frequencies. A mechanical hand was built for experiments to simulate human hand tremors with repeatability at a fixed frequency. The magnitudes and frequencies of the tremors in the mechanical hand were quantitatively identified using the inductive sensor. Hence, feasibility and accuracy of the contactless hand tremor detector were determined. A triaxial accelerometer was used for comparison. By comparing spectral distributions and magnitudes of the tremors, the inductive sensor performed better than the accelerometer. The detector was applied to evaluate actual hand tremors of three subjects who had undergone exercise to induce tremors. The tremor waveform amplitudes of the subjects were quantitatively analyzed by the standard deviations method. The increased signal energies of exercise-induced tremor within 8–12 Hz were confirmed. Then, a subject with early Parkinson’s disease was evaluated by the proposed hand tremor detector. The tremor magnitudes and frequencies of the patient hand were quantitatively identified within in 4–7 Hz. Therefore, the new contactless hand tremor detector can be developed as a clinical instrument for monitoring the fatigue symptoms of post-exercise and diagnosing the early Parkinson’s disease.     

Monitoring kidney and renal cyst volumes applying MR approaches on a rapamycin treated mouse model of ADPKD

Object  The aim of our study was to determine total cystic volume in a mouse model of PKD using MR imaging to monitor therapeutic effects in vivo. Materials and methods  We imaged eight female pcy-mice in two groups: four belonged to an untreated control group and four were treated with the anticystic agent rapamycin, which has proven to be effective in reducing cystogenesis in animal models. The mice were imaged using a 9.4 Tesla animal scanner. MRI measurements were taken at six time points during the therapy. Total renal volumes and total cyst volumes were calculated using a thresholding approach. Results  During the course of the treatment, the total cyst volume increased significantly faster than the total renal volume in the untreated group, indicating that growth of the total renal volume in the untreated group was primarily due to the growth of the cysts, rather than the parenchyma. The measured total renal volume in the control (placebo) group was significantly higher than the volume in the treated group. Conclusion  Using MRI, we were able to monitor the cystic volume in a mouse model of PKD to assess the therapeutic effect of anticystic treatment.     

Scherfließen und Wandgleiten von Massen für den Pulverspritzguss

This contribution presents coupling of laws for shear flow and wall slipping by the shear stress at the slipping interface. It includes the special case of Coulombian friction postulated by Uhland as well as the assumption of a constant sliding velocity along the flow channel according to Mooney. As an example, Ostwald and de Waele's law of shear thinning flow is combined with a shear stress of sliding depending on internal pressure by a power law. Examined feedstocks for metal injection molding showed a rheological behavior according to the model presented.     

Vorkalkulation chemischer Anlagen

The economic analysis of processes allows a market orientation and prioritization of development projects. First of all, a preliminary costing takes place by estimating the investment costs. Basis for calculation is a complete process flow diagram with mass and energy balances for a layout of the process steps, performed in the standard material AISI 316Ti. Costs of other materials can be calculated with factors from a table, that of the other sizes and capacities by degression exponents. The preliminary costing is exemplified. The investment is the basis for the subsequent calculation of production costs.