Passive room conditioning using phase change materials—Demonstration of a long-term real size experiment

The thermal properties of lightweight buildings can be efficiently improved by using phase change materials (PCMs). The heat storage capacity of the building can be extended exactly at the desired temperature level, which leads to an enormous increase in residential comfort. This is shown in the present paper using the example of a prefabricated wooden house. The house was divided into two identical rooms. One of them was equipped with almost one ton of phase change material based on salt hydrates with a melting temperature of approx. 21°C. The material was encapsulated in 1-l Polyethylene containers and installed in two back-ventilated layers inside of the walls. The house was monitored for a period of 87 days in terms of temperatures, solar radiation and air velocity inside the PCM wall system. A considerable temperature buffering could be observed in the PCM room compared to the reference room. An overall reduction of the temperature fluctuations of 57% and a reduction of the day/night fluctuations of 62% compared to the reference room could be obtained. In addition, a prediction regarding the energy demand of such buildings is discussed on the basis of a simulation program. Thus, the annual cooling capacity can be reduced by 36.5% compared to the regular timber construction technique by introducing PCM. Furthermore, the good correlation of the simulation results with the experimental ones allows using the simulation as a tool to design a house with additional thermal storages.     

Study of CDM specific effects for a smart power input protection structure

A Charged Device Model (CDM) specific ESD failure mechanism is discussed for an input protection structure in a smart power technology. The input structure shows unexpected dependency of the CDM robustness on design variations of the input resistor. This paper demonstrates that circuit simulation reproduced the complex failure mechanism accurately after elements like package parameters, substrate resistance, parasitic pn-junctions and the resistance of parasitic physical layers were considered. The importance of accurately modeling these factors for achieving meaningful conclusions for CDM failure mechanisms and CDM robustness from circuit simulation is presented. For validation of the proposed simulation setup, results from circuit simulation are compared to measurements and device simulation.     

On the decomposition of the 0.6LiBH4-0.4Mg(BH4)2 eutectic mixture for hydrogen storage

The dehydrogenation reaction of the 0.6LiBH₄-0.4Mg(BH₄)₂ eutectic system was investigated by Temperature-Programmed-Desorption and Pressure-Composition-Isotherm methods, in the range of 25–540 °C and 0.1–150 bar of p(H₂). A sequence of four decomposition steps was found by TPD measurements; they occur at 235, 315, 365 and 460 °C for p(H₂) = 3 bar, with a clear T decrease with respect to pure LiBH₄ and Mg(BH₄)₂. In the PCI experiments, the first two steps could not be resolved but appeared merged in a single process. The amounts of H₂ release at each step and the Δ_rH and Δ_rS values derived from van’t Hoff plots were analyzed and compared with known results for relevant possible reactions. A scheme of interpretation was then proposed for all four processes. In particular, a fraction of LiBH₄ and Mg(BH₄)₂ would react together in the range of 300–350 °C according to 2LiBH₄ + Mg(BH₄)₂ → 2B + 2LiH + MgB₂ + 7H₂, thus explaining the quite large H₂ yield therein observed. The first and fourth steps correspond to decompositions of pure remaining Mg(BH₄)₂ and LiBH₄, respectively, and the third one to dehydrogenation of MgH₂ produced in the first step.     

Modified synthesis of [Fe/LiF/C] nanocomposite, and its application as conversion cathode material in lithium batteries

In an attempt to enhance the energy storage capacity and discharge voltage, a new cathode material based on ferrocene and LiF for lithium-ion batteries has been explored [Fe/LiF/C] nanocomposite (1) has been synthesized by pyrolysis of a ferrocene/LiF mixture at 700 °C using a rotating quartz tube setup in a furnace. The structure and morphology of the composite were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Brunauer-Emmer-Teller (BET) analysis, Raman, and Mössbauer spectroscopy. The nanocomposite is composed of well-defined nanotubes which are interlinked by graphitic shell-type structures containing uniformly distribution of Fe, Fe-C, and LiF nanoparticles. The binder-free nanocomposite cathode showed enhanced electrochemical performance with the reversible specific capacity of 230 mAh g⁻¹ (1.3-4.3 V) at 20.8 mA g⁻¹ at room temperature. It exhibited a remarkable cyclic stability and good rate capability performances. The morphology of 1 was changed by ball milling, and the resulting nanocomposite 2 did not show any cyclic stability as a cathode. Thus, the cyclic stability and rate capability performances of 1 were attributed to its structure and morphology.     

Maximum Active Concentration of Ion-Implanted Phosphorus During Solid-Phase Epitaxial Recrystallization

In this paper, we showed that the maximum active P concentration of approximately 2 times10²⁰ cm^-3 exists during solid-phase epitaxial recrystallization (SPER). This maximum active concentration is close to the reported values for other active impurity concentrations during SPER. We introduced the concept of an isolated impurity that has no neighbor impurities with a certain lattice range. Assuming that impurities interact with three or four neighbor impurities, we can explain the activation phenomenon during SPER. According to our model, the isolated P concentration N _iso has a maximum value of approximately 2 times10²⁰ cm^-3 at a total impurity concentration of approximately 10²¹ cm^-3, and it decreases with a further increase in total impurity concentration. Deactivation occurs after the completion of SPER with increasing annealing time, and the active impurity concentration decreases with time but is always higher than the maximum diffusion concentration N _{Diff max}. We also observed that N _{Diff max} is independent of the annealing time despite nonthermal activation in the high-concentration region. We evaluated the dependence of N _{Diff max} on annealing temperatures. We think that this N _{Diff max} can be regarded as the electrical solid solubility N _Esol that the active impurity concentration reaches in thermal equilibrium. We observed the transient enhanced diffusion (TED) after the completion of SPER, and that, the deactivation process continues during and after TED, and the corresponding diffusion coefficient is still much higher than that in thermal equilibrium even after TED has finished, which suggests that the deactivation process releases point defects.     

On negative differential resistance in hydrodynamic simulation of partially depleted SOI transistors

We show that the negative differential resistance in the I/sub d/-V/sub ds/ characteristics observed in hydrodynamic transport simulations of partially depleted silicon-on-insulator MOSFETs disappears if the nonlocality of tunneling effects are properly accounted for in the recombination-generation process.     

High‐Temperature Photochromism of Fe‐Doped SrTiO3 Caused by UV‐Induced Bulk Stoichiometry Changes

The impact of UV irradiation on Fe‐doped SrTiO₃ (Fe:STO) single crystals is investigated at elevated temperatures. Illumination leads to incorporation of oxygen into the single crystals and thus to a decreasing oxygen vacancy concentration and oxidation of Fe³⁺ to Fe⁴⁺. The Fe⁴⁺ ions cause a color change from transparent/brownish to black. This photochromic blackening due to stoichiometry changes at elevated temperatures is irreversible at room temperature, but annealing at high temperatures, for example at 700 °C, can restore the original stoichiometry and color. Absorbance changes due to UV irradiation are monitored by ex situ and in situ UV–vis spectroscopy experiments and changes in electrical properties are measured by van der Pauw measurements and in‐plane electrochemical impedance spectroscopy. After 1140 min of illumination at 440 °C, for example, electrical measurements reveal a conductivity increase by more than a factor of 5 due to the enhanced hole concentration in blackened Fe:STO. In addition, UV illumination increases the oxygen chemical potential up to a calculated p(O₂) of more than 10⁹ Pa in Fe:STO. Hence, UV light can be used to tune the color, but also electrical properties of Fe:STO by directly impacting the bulk defect concentrations.     

Capillary Nanostamping with Spongy Mesoporous Silica Stamps

Classical microcontact printing involves transfer of molecules adsorbed on the outer surfaces of solid stamps to substrates to be patterned. Spongy mesoporous silica stamps are prepared that can be soaked with ink and that are topographically patterned with arrays of submicron contact elements. Multiple successive stamping steps can be carried out under ambient conditions without ink refilling. Lattices of fullerene nanoparticles with diameters in the 100 nm range are obtained by stamping C₆₀/toluene solutions on perfluorinated glass slides partially wetted by toluene. Stamping an ethanolic 1‐dodecanethiol solution onto gold‐coated glass slides yields arrays of submicron dots of adsorbed 1‐dodecantethiol molecules, even though macroscopic ethanol drops spread on gold. This outcome may be related to the pressure drop across the concave ink menisci at the mesopore openings on the stamp surface counteracting the van der Waals forces between ink and gold surface and/or to reduced wettability of the 1‐dodecanethiol dots themselves by ethanol. The chemical surface heterogeneity of gold‐coated glass slides functionalized with submicron 1‐dodecanethiol dots is evidenced by dewetting of molten polystyrene films eventually yielding ordered arrays of polystyrene nanoparticles.     

An attempt to model the human body as a communication channel

Using the human body as a transmission medium for electrical signals offers novel data communication in biomedical monitoring systems. In this paper, galvanic coupling is presented as a promising approach for wireless intra-body communication between on-body sensors. The human body is characterized as a transmission medium for electrical current by means of numerical simulations and measurements. Properties of dedicated tissue layers and geometrical body variations are investigated, and different electrodes are compared. The new intra-body communication technology has shown its feasibility in clinical trials. Excellent transmission was achieved between locations on the thorax with a typical signal-to-noise ratio (SNR) of 20 dB while the attenuation increased along the extremities.