Electrical and Photoresponse Properties of Al/p-Si/Y 1-x Sr x MnO 3 /Al Heterojunction Photodiodes

The electrical and photoresponse properties of Al/p-Si/Y1-xSrxMnO3/Al diodes were investigated by using current-voltage and transient photocurrent measurements. The average ideality factor and barrier height has been calculated as 4.2568 and 0.613 eV respectively. The calculated ideality factor for Al/p-Si/Y1-xSrxMnO3/Al diodes is higher than unity because of the interface states, native oxide layer and series resistance. Also, diodes have exhibited property of photosensitivity. These indicated that the fabrication of diodes can be used optoelectronic device applications.     

Magnetic resonance imaging at 9.4 T: the Maastricht journey

The 9.4 T scanner in Maastricht is a whole-body magnet with head gradients and parallel RF transmit capability. At the time of the design, it was conceptualized to be one of the best fMRI scanners in the world, but it has also been used for anatomical and diffusion imaging. 9.4 T offers increases in sensitivity and contrast, but the technical ultra-high field (UHF) challenges, such as field inhomogeneities and constraints set by RF power deposition, are exacerbated compared to 7 T. This article reviews some of the 9.4 T work done in Maastricht. Functional imaging experiments included blood oxygenation level-dependent (BOLD) and blood-volume weighted (VASO) fMRI using different readouts. BOLD benefits from shorter T₂* at 9.4 T while VASO from longer T₁. We show examples of both ex vivo and in vivo anatomical imaging. For many applications, pTx and optimized coils are essential to harness the full potential of 9.4 T. Our experience shows that, while considerable effort was required compared to our 7 T scanner, we could obtain high-quality anatomical and functional data, which illustrates the potential of MR acquisitions at even higher field strengths. The practical challenges of working with a relatively unique system are also discussed.

     

Fe-Cu coated nickel mesh usage as cathode catalyst for hydrogen evolution reaction

Nickel mesh electrodes were used as the working electrode. Iron and copper were electrochemically deposited on the nickel mesh in different amounts. When electrochemical coatings had been carried out, different currents were passed from the circuit at different times and coatings were accumulated at constant load. The prepared electrodes called as FexCux, FexCu3x and FexCu9x and these electrodes have been used for hydrogen evolution reaction (HER). The surface morphologies were investigated by scanning electron microscopy. The HER activity is assessed by recording cathodic current–potential curves, cyclic voltammetry, electrochemical impedance spectroscopy. The results show that FexCu9x catalysts have a compact and porous structure as well as good electrocatalytic activity for the HER in alkaline media.     

Utilization of nanoindentation to examine bond line integrity in adhesively bonded composite structures

This study explores the probable correlation between degradation in bond line fracture toughness and the changes in the measurable mechanical properties of the adhesive layer due to environmental contamination in adhesively bonded composite structures. Nanoindentation technique is utilized to measure the adhesive Young’s modulus and hardness. The proposed framework utilizes the large scale bridging of interfacial fracture proposed by Tvergaard and Hutchinson (Philos Mag A 70(4):641–656, 1994), for considering the significant contribution of plasticity on the macroscopic bond line fracture toughness. A typical adhesive-adherend material system (EA9394/Hexcel IM7-G/8552) exposed to different contaminants at the same concentration is examined. Hardness measurements showed two distinct effects of contamination on the adhesive material; namely (1) softening and (2) hardening depending on the class of contaminants. In addition, macroscopic mode-I fracture toughness is independently measured by double cantilever beam test. Finite element method employing cohesive zone method is used to rationalize the experimental results and the prospective scaling-laws. The combined experimental results of macroscopic properties and the numerical results of the interfacial properties showed the role of contamination in reducing the plastic dissipation within the bond line and the macroscopic deterioration of the bond line effective fracture toughness. The results showed the existence of a correlation similar to Tvergaard and Hutchinson’s results. However, the results suggest a scaling between the interfacial cohesive fracture toughness and the measurable flow stress. The scaling correlation has the potential to be utilized in assessing the relative trend between different contaminants. While the proposed scaling is verified for a common adhesive-adherend system in aerospace industry, with additional examination of other systems, the proposed scaling law might facilitate the utilization of the perceived non-destructively evaluated indentation hardness to serve as an indicator for the bond line macroscopic fracture toughness.