Real-space imaging of inelastic Friedel-like surface oscillations emerging from molecular adsorbates

We report real space imaging measurements of inelastic Friedel oscillations. The inelastic electron tunneling spectroscopy, using scanning tunneling microscopy, around dimers of dichlorobenze adsorbates on Au(111) surface display clear spatial modulations that we attribute to inelastic scattering at the molecular sites caused by molecular vibrations. Due to local interactions between the adsorbate and the surface states, the molecular vibrations generate a redistribution of the charge density at energies in a narrow range around the inelastic mode. Our experimental findings are supported by theoretical arguments.     

Charge Transport Through a Cardan‐Joint Molecule

The charge transport through a single ruthenium atom clamped by two terpyridine hinges is investigated, both experimentally and theoretically. The metal‐bis(terpyridyl) core is equipped with rigid, conjugated linkers of para‐acetyl‐mercapto phenylacetylene to establish electrical contact in a two‐terminal configuration using Au electrodes. The structure of the [Ru^II( L )₂](PF₆)₂ molecule is determined using single‐crystal X‐ray crystallography, which yields good agreement with calculations based on density functional theory (DFT). By means of the mechanically controllable break‐junction technique, current–voltage (I–V), characteristics of [Ru^II( L )₂](PF₆)₂ are acquired on a single‐molecule level under ultra‐high vacuum (UHV) conditions at various temperatures. These results are compared to ab initio transport calculations based on DFT. The simulations show that the cardan‐joint structural element of the molecule controls the magnitude of the current. Moreover, the fluctuations in the cardan angle leave the positions of steps in the I–V curve largely invariant. As a consequence, the experimental I–V characteristics exhibit lowest‐unoccupied‐molecular‐orbit‐based conductance peaks at particular voltages, which are also found to be temperature independent.     

Gas pressure measurements during continuous hot pressing of particleboard

Knowledge about the development of the internal gas pressure during hot pressing of wood-based composites is important for the optimization of panel properties and production speed. The gas pressure heavily affects the thermodynamic conditions inside the wood furnish mat, and a too high maximum value at press opening might cause an impairment of the panel properties. In this paper, gas pressure and temperature measurements inside a particle mat while passing through a continuous hot press are presented for the first time. The measurements were performed with a transportable system, consisting of a steel tube attached to a miniature pressure transducer and a data logger. The particleboards had a target thickness of mainly 16 mm, but also of 28 mm and 38 mm, respectively. The measurements show a distinct horizontal gas pressure distribution in both directions, in production direction and across the mat’s width. In contrast, cross-sectional gas pressure gradients were only visible inside the panels after leaving the press. By comparing the gas pressure curves measured for particleboard with those for medium density fiberboard (MDF), characteristic differences became evident. Overall, the gas pressure is higher in MDF compared to particleboard. Finally, a comparison between the gas pressure levels measured for three different panel thicknesses showed a clear relation between panel thickness and gas pressure, with a decreasing panel thickness resulting in an increase in gas pressure. The results of this paper will contribute to our understanding about the events inside wood furnish mats during continuous hot pressing.     

Thermal response testing of a fractured hard rock aquifer with and without induced groundwater flow

This study quantifies experimentally the influence of groundwater on the thermal conductivity measurements via thermal response tests (TRT) in a fractured hard rock with low matrix permeability. An artificial groundwater flow towards a nearby well was induced by groundwater extraction and a TRT performed simultaneously. The results were compared with a TRT performed 24?days later in the same well without groundwater extraction. The effect of the groundwater flow is shown indirectly by the enhanced effective thermal conductivity and directly through the comparison of temperature profiles before and 4?h after both TRTs. Simulations in FEFLOW show that a groundwater flow velocity of 130–1,300?m?d^?1 through one open horizontal fracture of small volume increases the effective thermal conductivity by 11?% in the studied system.     

A Novel PowderMEMS Technique for Fabrication of Low-Cost High-Power-Factor Thermoelectric Films and Micro-Patterns

Thermoelectric (TE) films, which are normally fabricated by MicroElectroMechanical-Systems (MEMS) technology, are crucial for the development of micro-TE devices (e.g., Peltier coolers for hot-spot cooling, TE generators). However, achieving a significant TE property (e.g., high power factor) of TE films and a low-cost fabrication process is challenging. A novel fabrication technique named PowderMEMS to fabricate high-performance, low-cost TE films, and micro-patterns is presented in this article. The TE film is based on agglomeration of micro-sized N-type ${\text{Bi}}_2{\text{Te}}_{2.5}{\text{Se}}_{0.5}$(BTS) powders with stoichiometric composition by the molten binder bismuth (Bi). The influence of the key process parameters (e.g., the weight ratio between the TE powder and the binder, the hot-pressing duration, and pressure) on the TE performance is investigated. The TE film exhibits a maximum power factor of 1.7 ${\text{mW m}}^{-1}{\mathrm{K}}^{-2}$ at room temperature, which is the highest value reported so far for the state-of-the-art TE thick film (thickness > 10 μm). Besides, the PowderMEMS-based TE films are successfully patterned to the micro-pillar array, which opens up a new MEMS-compatible approach for manufacturing micro-TE devices.