Electrode effects in the sweeping of alpha quartz

Experimental observations are described in the air-sweeping of alpha-quartz that reveal the introduction of hydrogen. Porous electrodes facilitate the indiffusion of hydrogen. By contrast, the use of thick, nonporous, strongly adherent Au/Cr electrodes causes a color-center front to advance from anode to cathode. Evidence is presented that indicates that: (1) color centers form beneath nonporous portions of the anode that correlate with the formation of Cr(2)O(3) on the metal surface and Cr-silicides at the metal-quartz interface, and (2) large-diameter clear striae form along the c-axis that correlate with small openings in the anode. These observations suggest that: (1) openings in the anode metallization are required for hydrogen introduction; (2) the electrochemical charge-transfer reaction, leading to hydrogen introduction, occurs at the gas-electrode-quartz boundary and spreads laterally by interfacial diffusion of hydrogen species; and (3) color centers form through the suppression of interfacial H-diffusion. Additionally, electrode-surface damage and high electric fields can result in undesirable electrode-metal indiffusion.     

Testing of timber structures and building boards

RILEM Recommendations57-TSB RILEM/CIB Joint Technical Committee

Testing of timber structures and building boards     

Metallurgical interactions at the contacts GaAs interface

Interface morphology, phase composition, and elemental diffusion of Pt/Ti/Ge/Pd ohmic contacts to both n and p⁺-GaAs have been investigated as a function of annealing temperature. Structural and chemical results were correlated with specific contact resistances (ρ_c) measured for each thermal treatment. Annealing at 450°C yielded the lowest ρ_c, ～6.4 × 10^?7Ω-cm². The interface was observed to be smooth and abrupt. Two interface phases were detected; a primary phase, PdGe, and a secondary, Ga-rich Pd-Ga-As ternary phase. The presence of this ternary phase was found to be critical to contact formation on n-GaAs. The Ti and Pt layers remained pristine. Annealing at 550°C resulted in a slightly higher ρ_c, ～2.1 × 10^?6Ω-cm². There was significant elemental diffusion within the contact metal and minor diffusion into the GaAs substrate. The interface possessed limited areas of spiking with uniform composition. Annealing at 600°C proved to have a detrimental effect on the ρ_c, ～10^?4Ω-cm². This electrical degradation was accompanied by strong chemical intermixing between the contact and substrate, resulting in a continuous nonplanar interface with deep multiphase protrusions.     

Development of a TES-Based Anti-coincidence Detector for Future x-Ray Observatories

Microcalorimeters onboard future x-ray observatories require an anti-coincidence detector to remove environmental backgrounds. In order to most effectively integrate this anti-coincidence detector with the main microcalorimeter array, both instruments should use similar read-out technology. The detectors used in the Cryogenic Dark Matter Search (CDMS) use a phonon measurement technique that is well suited for an anti-coincidence detector with a microcalorimeter array using SQUID readout. This technique works by using a transition-edge sensor (TES) connected to superconducting collection fins to measure the athermal phonon signal produced when an event occurs in the substrate crystal. Energy from the event propagates through the crystal to the superconducting collection fins, creating quasiparticles, which are then trapped as they enter the TES where they produce a signal. We are currently developing a prototype anti-coincidence detector for future x-ray missions and have recently fabricated test devices with Mo/Au TESs and Al collection fins. We present results from the first tests of these devices which indicate a proof of concept that quasiparticle trapping is occurring in these materials.     

Properties and application of TRIP‐steel in sheet metal forming

A further development of dual‐phase‐steels are represented by TRIP (transformation induced plasticity) ‐steels. TRIP‐steels contain austenite, which is metastable at room temperature. It transforms to martensite during straining (TRIP effect). This process improves the strength‐ductility balance of these steels. Two types of TRIP‐steels, low alloyed (L‐TRIP) and high alloyed (H‐TRIP), can be applied in sheet forming processes and exhibit different forming characteristics. Basing on results of uniaxial tensile tests and the evaluation of Young's modulus the forming limits in deep drawing processes and the component properties of deep drawn parts are discussed. The Young's modulus decreases significantly with increasing pre‐strain, especially demonstrated for the L‐TRIP material TRIP700. Forming limit curves determined at different forming temperatures indicate its influence on the forming limits. Martensite transformation is suppressed at a temperature of approximately T = 200 °C and therefore the major strain ?₁ decreases significantly. For the investigated stainless steel AISI304 (H‐TRIP) different lubricant types in comparison to chlorinated paraffins have been tested. Lubricants consisting of sulphur additives led to good forming conditions in forming processes, even better than lubricants based on chlorinated paraffins. The evaluation of component properties, compared between L‐TRIP and H‐TRIP, was done based on the analysis of springback and dent resistance. The L‐TRIP material TRIP700 shows higher springback angles than AISI304 resulting from higher yield strength and decreased Young's modulus, resulting from the forming process. The dent resistance of TRIP‐steel was exemplarily demonstrated for AISI304. Uniaxial pre‐strained sheet specimen were analysed to show the dent resistance depending on dent depth. During elastic denting pre‐strain has no influence on dent resistance. Further increasing dent depth lead to increased dent forces for pre‐strained specimens.     

Characterization and Performance of Magnetic Calorimeters for Applications in X-ray Spectroscopy

We have developed prototype arrays of metallic magnetic calorimeters for applications in X-ray astronomy. Each pixel consists of an all-gold X-ray absorber in good thermal contact to a gold-erbium paramagnetic thin film thermometer that is operated in the temperature range of 30–100 mK. The para-magnetic response is coupled to a SQUID amplifier. We have characterized pixels in an array and observed the expected temperature dependence of the magnetization and heat capacity. We have demonstrated a full width at half maximum energy resolution of 1.7  \(\pm \) 0.1 eV at 6 keV and have also read out these devices using time-division multiplexing.     

Discontinuous Galerkin solution of a phase-field model in isothermal chemical vapor infiltration of SiC

The microstructure evolution of the isothermal chemical vapor infiltration (ICVI) of silicon carbide (SiC) from methyltrichlorosilane (MTS) is simulated by a phase-field model which is implemented numerically using the discontinuous Galerkin method. The model consists of a phase-field equation describing the diffusive interface kinetics and a species transport equation describing the mass balance. For the diffusive interface kinetics, a new form of the free energy density related to the ICVI process is adopted to ensure two stable states of gas phase and solid phase, and the Gibbs free energy changing between these two phases is taken as driving force. For the mass balance, two process intensities depending on the phase-field parameter are introduced to account for the homogeneous gas reaction and the heterogeneous surface reaction including the influence of the by-product hydrogen chloride (HCl). Finally, a discontinuous Galerkin formulation is derived for the nonlinear phase-field model and a priori error analysis is used for the semi-discontinuous formulations based on the proof of the uniqueness of the solution of the discontinuous approximation. Two numerical examples are presented to demonstrate the validity of the discontinuous Galerkin method and to investigate the effect of geometric parameters on microstructure evolution.     

AHAPS-functionalized silica nanoparticles do not modulate allergic contact dermatitis in mice

Allergic contact dermatitis (ACD) is a common skin disease in people and may become a potential site of exposure to nanoparticles (NP). Silica nanoparticles (SiO₂-NP) possess a promising potential for various medical and non-medical applications, including normal and diseased skin as target organs. However, it has been shown that negatively charged SiO₂-NP may act as proinflammatory adjuvant in allergic diseases. The effect of topical SiO₂-NP exposure on preexisting ACD has not been studied to date although this reflects a common in vivo situation. Of particular interest are the potential effects of positively charged N-(6-aminohexyl)-aminopropyltrimethoxysilane (AHAPS)-functionalized SiO₂-NP which are promising candidates for delivery systems, including gene delivery into the skin. Here, the effects of such AHAPS-functionalized SiO₂-NP (55 ± 6 nm in diameter) were studied in an oxazolone-induced ACD model in SKH1 mice and compared to ACD mice treated with vehicle only. The clinical course of the disease was assessed by monitoring of the transepidermal water loss (TEWL) and the erythema. In histologic and morphometric analyses, the distribution of particles, the degree of inflammation, epidermal thickness, and the inflammatory infiltrate were characterized and quantified by standard and special histological stains as well as immunohistochemistry for CD3+ lymphocytes. To assess possible systemic effects, serum immunoglobulin E (IgE) was determined by enzyme-linked immunosorbent assay. Following administration of AHAPS-SiO₂-NP for five consecutive days, no effects were observed in all clinical, histologic, morphometric, and molecular parameters investigated. In conclusion, positively charged AHAPS-SiO₂-NP seem not to affect the course of ACD during exposure for 5 days.     

Thermal issues in machine tools

This paper presents a review of the latest research activities and gives an overview of the state of the art in understanding changes in machine tool performance due to changes in thermal conditions (thermal errors of machine tools). The topics are focused on metal cutting machine tools, especially on turning and milling machines as well as machining centres. The topics of the paper thermal issues in machine tools include measurement of temperatures and displacements, especially displacements at the tool centre point, computations of thermal errors of machine tools, and reduction of thermal errors. Computing the thermal errors of machine tools include both, temperature distribution and displacements. Shortly addressed is also to avoid thermal errors with temperature control, the influence of fluids and a short link to energy efficiency of machine tools. The paper presents the summary of research work in the past and current. Research challenges in order to achieve a thermal stable machine tool are discussed. The paper apprehend itself as an update and not a substitution of two published keynote papers of Bryan et al. [28] in 1990 and Weck et al. [199] in 1995.