Hydrogen storage in MgH2LaNi5 composites prepared by cold rolling under inert atmosphere

Mg-AB₅ composites are promising systems for hydrogen storage applications, due to their possibility of hydrogen cycling at relatively low temperatures. Traditionally, these composites are mainly processed by high-energy ball milling (HEBM) techniques employing longer processing times. In this study, cold rolling was applied to prepare MgH₂LaNi₅ composites and the hydrogen storage properties were investigated. The materials were processed using a vertical rolling mill under argon atmosphere, leading to a good homogeneity and no contamination at shorter processing times. The mixture of MgH₂-1.50 mol.% LaNi₅ showed the best hydrogen storage properties at 200 °C and 100 °C and the lowest desorption temperature even when compared to cold rolled MgH₂. The results indicate that the composite MgH₂LaNi₅ is transformed into a mixture of three phases MgH₂, Mg₂NiH₄ and LaH₃ upon hydrogen absorption/desorption cycles. The synergetic effect among these phases when in appropriate proportion in the sample seems to play a crucial role in the acceleration of hydrogen absorption/desorption kinetics at lower temperatures in comparison to MgH₂.     

Vereisung von Kabeln

Aerodynamische Instabilität von Seilen als Folge eines durch Eisablagerungen geänderten Querschnitts ist ein bekanntes Phänomen. Da die experimentelle Untersuchung von Vereisungsvorgängen sehr aufwendig ist, soll hier ein numerisches Vereisungsmodell vorgestellt werden. Das numerische Modell besteht aus zwei Berechnungsschritten: Zunächst wird die Strömung aus Luft und Niederschlagspartikeln als einfach gekoppelte Zweiphasenströmung berechnet. Basierend auf dem Massestrom der Niederschlagspartikel wird dann das Eiswachstum ermittelt. Die neue Geometrie dient dann als Grundlage für die nächste Strömungsberechnung. Ice accretion on cables. Aerodynamic instability of cables due to ice accretion is a known phenomenon. Investigating the shape and density of the ice accretion by experiments is very complex. Therefore a numerical model is presented to simulate ice accretion processes on cables. The model is divided into two main parts, the calculation of the flow field and the ice accretion. The stream of air and precipitation particles is modeled as a one‐way coupled multiphase flow. Ice accretion and flow field are calculated iteratively to account for geometrical changes of the ice deposit in the flow calculation.     

Dimensional Changes in CFRP/PMI Foam Core Sandwich Structures

A sandwich structure was observed from the beginning of life—starting at the vacuum assisted manufacturing process up to several environmental in service conditions. Strain variations due to curing process at the manufacturing, well as thermal fluctuations and humidity environments in service were detected and reviewed by their influence on the overall dimensional stability. The CFRP/PMI foam core sandwich structure was checked for an application as a primary structure in commercial aviation with its specific environmental requirements.     

Supplier development: communication approaches,activities and goals

Operations managers rely on the purchasing function to obtain production inputs from suppliers and to ensure supplier performance. The link between supplier development activities performed by buying firms with their suppliers, in terms of operational outcomes and impact on competitive advantage for the buying firm has been well documented. However, a buying firm should, prior to setting up a supplier development program and investing in supplier development activities, establish goals it wants to achieve and determine how to achieve these goals. Until now, supplier development goals in general and their relationship with supplier development activities have received little research attention. The results from this empirical study suggest that the relationship between the goal to improve a supplier's capabilities and knowledge transfer from the buyer to the supplier firm is moderated by the degree of human interaction. Buying firms pursuing the strategy to improve supplier capabilities rely more intensively on training and co-location of buyer and supplier employees to leverage the knowledge transfer to the supplier firm.     

The influence of different knowledge workers on innovation strategy and product development performance in small and medium-sized enterprises

Despite significant interest on the topic of knowledge workers, the understanding of how they influence certain aspects of firm innovativeness remains limited. In particular, while different types of knowledge workers exist, their particular synergistic effects on new and improved product development within smaller firms has received less attention. Drawing on the knowledge-based view (KBV), we posit that innovation strategy plays an instrumental role in linking the effects of knowledge workers, thereby leading to greater product development outcomes from different types of knowledge workers. Moreover, some suggest that beyond a certain point, there is a diminishing return to increasing the proportion of knowledge workers in an organisation; however, the basis of this finding is within larger firms. This study investigates whether high-level (e.g. engineers and scientists) and low-level (e.g. technicians and machine operators) knowledge workers exert varying effects on performance in terms of new and improved product development. Data from 205 small and medium-sized high-tech manufacturing firms provide support that distinguishing among types of knowledge workers is important given that they impact new and improved product development differently. Furthermore, innovation strategy plays a synergistic role, positively mediating the effects of different types of knowledge workers on innovation outcomes.     

Trimethylsilane-based pretreatments in a Mg-rich primer corrosion prevention system

A trimethylsilane-based coating was investigated as a pretreatment for Al-2024 T3 in a novel Mg-rich primer corrosion prevention system. SiC-based thin films were deposited onto Al substrates by plasma-enhanced chemical vapor deposition (PECVD). A screening study of the pressure (P) dependence of films deposited at 350 °C showed an increase in growth rate from 0.6 to 1.9 Torr. A second screening study where P was fixed at 1.9 Torr and temperature (T) was varied from 125 to 550 °C showed decreasing growth rates with increasing temperature with an apparent transition around 300 °C. Electrochemical impedance spectroscopy (EIS) of the SiC-based films on Al-2024 after exposure to a corrosive environment (i.e., dilute Harrison solution) indicated that samples coated using SiC-based films exhibit higher low frequency impedance (i.e., 100–1000× higher) than bare Al-2024 with open circuit potential remaining 0.1 V higher for the former suggesting the SiC-based films slow the corrosion process. A Mg-rich primer was coated onto the SiC on Al-2024 with the galvanic function of the system determined by EIS. As compared to SiC on Al-2024, a similar behavior for the low frequency impedance was observed for the Mg-rich primer-coated samples with some films exhibiting 1E + 8 Ω at 0.1 Hz indicating a strong barrier property. Initial gas jet erosion using acrylic media indicates the Mg-rich primer coatings are removed in preference to the Si–C films—the first step toward demonstrating a permanent pretreatment. When successfully developed and optimized, the value of such a hard, protective coating is the reduction of a three-component coatings system (i.e., pretreatment, primer, and topcoat) to a two-component system (i.e., primer and topcoat).     

Experimental examination of the wear behaviour of the VAlN tool coating by strip drawing process

Resistance to wear, and therefore the lifetime of forming tools, can be increased by surface functionalisation using novel, multifunctional coatings. Thereby, the tribological requirements on the coating are an essential factor. Within the scope of the research work presented here, tribological examinations were carried out on a metastable vanadium aluminium nitride (VAlN) tool coating when drawing the high-strength sheet metal material DP 800. It was shown that the wear of the VAlN tool coating can already be determined at stable frictional behaviour (μ?<?0.085). The wear analysis was carried out considering the topography and change in hardness of the tool surface during the drawing path of 110,000?mm under a contact stress of 150?MPa.     

From contact angle titration to chemical force microscopy: a new route to assess the pH-dependent character of the stratum corneum

Despite of its complex multicomponent organization and its compact architecture, the Stratum corneum (SC) is not completely impermeable to substances directly applied on the skin surface. A huge number of works have been dedicated to the understanding of the mechanisms involved in substance permeation by exploring deeper layers than the SC itself. Surprisingly, there is a poor interest in studies relating to interactions which may occur in the near-surface region (i.e. approximately 1 nm depth) of the SC. In this work, equilibrium proton-transfer reactions have been used as probes to define in a fundamental point of view the nature of the SC interactions with its environment. Such titration curves are investigated on 'in vitro' SC (isolated SC from abdominal skin tissue) and on 'in vivo' volar forearm (a sebum poor area). The results are discussed in term of work of adhesion and surface pKa values. Because SC can 'reconstruct' under heating, influence of the temperature on titration curves is investigated and the role of the different components is discussed. Different sigmoidal transitions were observed. Two common pKa values (pKa(1) = 4 and pKa(2) = 11.5) were clearly identified in both cases and associated to an acid-base character. By playing with the temperature of 'in vitro' SC, the 'accessibility' of polar functions was increased, thus refining the results by revealing an amphoteric character with an acid-to-base transition at pH 3.5 and two acid transitions at pH = 6.5 and pH = 11.5. Adhesion forces between an Atomic Force Microscopy (AFM) tip and a single isolated corneocyte through buffered liquid media were also investigated to better understand the role of the individual corneocytes.