Energy transduction ferroic materials

Ferroic materials and multiferroics, characterized by their ferroic orders, provide an efficient route for the coupling control of magnetic, mechanical, and electrical subsystems in energy transduction, which aims at converting one form of energy into another. A surge of interest in the ferroic coupling effect has stemmed from its potential use as a new versatile route for energy transduction. Here, the recent progress on the use of (multi)ferroic materials is reviewed, with special emphasis on the fundamental mechanisms that dictate the energy transduction process, including piezoelectricity, pyroelectricity, electrocaloric, magnetostriction, magnetocaloric, elastocaloric, magnetoelectricity, and emerging spin-charge conversion. Research on energy transduction ferroic materials paves the way for ubiquitous energy harvesting through magneto-mechano-electric-thermal coupling mechanisms. Finally, a summary and the future prospective directions of this field are discussed.     

Effiziente Herstellung von Kohlenstofffasern

Efficient production of carbon fibres using new technologies Innovative process technologies for carbonization of precursor fibres, which can substitute conventional oven technologies and raise the efficiency of carbon fibre production are presented. The process technologies are based on the substitution of convective heat transfer by microwave plasma or direct fiber heating. In microwave-assisted plasma treatment, the heating of the fibres is carried out both by microwave absorption in the fibre volume and energy input into the fibre surface by means of the plasma species. During electrical carbonization, the fibres are heated by means of an electrical current flow. The processes can be used separately, one after the other (also in combination with conventional furnace technology) or as hybrid processes.     

Joining of reaction-bonded silicon carbide using a preceramic polymer

Ceramic joints between reaction-bonded silicon carbide (RBSiC) were produced using a preceramic polymer (GE SR350 silicone resin) as joining material; samples were heat treated in an argon flux at temperatures ranging from 800–1200°C without applying any pressure. The strength of the joints was determined by four-point bending, shear and indentation tests. Microstructural and microchemical analyses were performed by optical microscopy, SEM, TEM and AEM. The room-temperature strength of the joints increased with the joining temperature. Maximum values as high as 220 MPa in bending and 39 MPa in shear tests were reached for samples joined at 1200°C. No detectable residual stresses were observed both in the joining material and the joined parts, and the fracture mechanism was nearly always cohesive. The joint thickness was shown to depend on the processing temperature, and ranged from about 2–7 m. The joining material was a silicon oxycarbide amorphous ceramic, with no oxygen diffusion occurring between this and the RBSiC joined parts. The lack of compositional gradients, precipitates or reaction layers indicate that the SiOC ceramic acted as an inorganic adhesive, and that the joining mechanism involved the direct formation of chemical bonds between the RBSiC parts and the joining material. © 1998 Chapman & Hall     

Kinetic and Mechanistic Studies of the Ozonation of Alicyclic Amines

Studies about the ozonation of the polar and mobile alicyclic amines pyrrolidine, piperidine, morpholine and piperazine were carried out in model water at pH 7.0. According to a pseudo-first order rate law the reaction-rate constants were determined from the decrease of the amine concentration vs. the reaction time. The order of degradation of the alicyclic amines by ozone, resulting from the kinetic constants obtained, is piperazine > morpholine ? piperidine > pyrrolidine. The pH value of the water, the chemical structure of the amines and their pK_A values are recognized to be parameters influencing the reactionrates of the amines.     

Quantitative representation of the anisotropy and tension/compression asymmetry of the critical resolved shear stress of an L12-ordered intermetallic

The anomalous anisotropy and tension (t)/compression (c)-asymmetry of the critical resolved shear stress τ_o of the L1₂-long-range ordered intermetallic γ′_NIM are analysed in the light of a published (Miner RV, Gabb TP, Gayda J, Hember, KJ. Met Trans A 1986; 17A: 507) analytical expression

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. Particles of γ′_NIM strengthen the commercial nickel-base superalloy NIMONIC 105. characterises the orientation of the specimen, and T_o≈300 K and T_peak≈ 1000 K mark the temperature (T) range in which τ_o is anomalous. Except for γ′_NIM-single crystals with the [011]-orientation, the formula describes the anisotropy and (t/c)-asymmetry of the critical resolved shear stress satisfactorily.     

Evaluation of a hybrid method for refrigerant flow balancing in multi-circuit evaporators

A companion paper [Kim, J.-H., Braun, J.E., Groll, E.A., 2009. A hybrid method for refrigerant flow balancing in multi-circuit evaporators: upstream versus downstream control. International Journal of Refrigeration doi:10.1016/j.ijrefrig.2009.01.013 presented a hybrid approach for providing control of refrigerant flow distribution in evaporators that involves the use of small balancing valves in each circuit along with a primary expansion device to control the overall superheat from the evaporator. Furthermore, the companion paper demonstrated that the flow balancing valves should be located upstream rather than downstream of the evaporator in order to realize significant benefits. The current paper utilizes the model presented in the companion paper to more fully evaluate the effects of uneven air and refrigerant flow distributions and the benefits of upstream hybrid control in response to these effects.     

Simulation of the current distribution in lead-acid batteries to investigate the dynamic charge acceptance in flooded SLI batteries

Measurements show that the dynamic charge acceptance (DCA) of flooded SLI lead-acid batteries during micro-cycling in conventional and micro-hybrid vehicles is strongly dependent on the short-term history, such as previous charge or discharge, current rate, lowest state of charge in the last 24 h and more. Factors of 10 have been reported. Inhomogeneous current distribution, especially as a result of acid stratification, has been suggested to explain the DCA variability.This hypothesis was investigated by simulation of a two-dimensional macrohomogeneous model. It provides a spatial resolution of three elements in horizontal direction in each electrode and three elements in vertical direction. For an existing set of parameters, different current profiles were analyzed with regard to the current distribution during charging and discharging.In these simulations, a strong impact of the short-term history on current, charge and acid density distribution was found as well as a strong influence of micro-cycles on both charge distribution and acid stratification.