The magneto-electric effect in molten salts—III. Measurement of the thermomagneto-electric effect in molten potassium nitrate

The joint action of two rectangular direct and constant fields (electric and magnetic) on molten potassium nitrate, produces local temperature variations in the Lorentz force direction. This thermal effect is studied as a function of the magneto-electric stress and also of the temperature of the molten electrolyte. The results are different depending on the initial thermal conditions; they are compared with the previous magneto-electric voltage measurements.     

Fabrication and mechanical analysis of mimosa tannin and commercial flax fibers biocomposites

Composites were prepared by impregnating commercial nonwoven and unidirectional flax fibers mats, with a mimosa tannin/hexamine resin without addition of NaOH as it was described in previous papers and with improved results. The influence of various parameters was observed: the curing cycle including temperature, time, pressure, the moisture content, and the number of fiber mats the composites were made of. A new two-step method was investigated: full drying of the pre-impregnated mats for storage first and then rehydratation just before pressing. The composites obtained gave good modulus of elasticity and tensile strength in traction as well as a good resistance to water swelling for composites prepared with 50% matrix resin/50% natural fibers. Best results appear to be obtained using a slow curing at low temperature (130?°C for 35?min) with moisture content of 20% on dry material.     

The magneto-electric effect in molten salts—2. Measurement of the magneto-electric voltage in some molten I-I inorganic salts: AgCl,KNO3 and NaNO3

The study of the magneto-electric effect on molten salts have been reported in a previous article in which were given the necessary conditions to measure a reproducible magneto-electric voltage and the results for an organic salt 1-ethylpyridinium bromide, in the molten state and in alcoholic and aqueous solutions, were compared. Here the study is extended to some inorganic II salts: silver chloride, potassium nitrate and sodium nitrate. A magneto-electric voltage is measured as a function of the magneto-electrics stress and also of the temperature of the molten salts. All the resulting graphs exhibited identical shapes and three characteristic parameters were noted which seemed to intercorrelate well. These results agree with those previously obtained from 1-ethylpyridinium bromide.     

The magneto-electric effect in molten salts—1. Visualization and measurement of the magneto-electric voltage in 1-ethyl-pyridinium bromide; comparison of results in the molten salt at 130 °C and in solutions in water and ethanol

The magneto-electric effect has been studied using 1-ethyl-pyridinium bromide in both the molten state and in solution in water or ethanol. The production of stable, coloured radical cations allows one to observe their movement in the cell. From the results it is possible to establish a relationship between the magneto-electric voltage and the type and behaviour of the electrolyte, to better understand the magneto-electric effect in ionic liquid media and to explain the apparent non-reproducibility of certain results. A Lorentz force causes a deviation in the trajectory of charge carriers. This deviation in current lines produces differences in charge concentration in the cell, particularly between the measurement probes. Thus the physical significance of the observed voltage is different from that of the Hall voltage described for electronic solid conductors.     

Electrodissolution de la galène en présence d'une induction magnétique inhomogéne

Résumé La polarisation anodique des sulfure de plomb en présence et en l'absence d'un champ magnétique a été étudiée en milieu d'acide chlorhydrique 1 mol dm^–3 à la temperature ambiante. Le courant anodique est sensible à la présence d'un champ magnétique inhomogène. Les études potentiocinétique et potentiostatique concernant l'influence de l'induction magnétique sur le courant montrent un comportement différent suivant la magnitude du champ. En choisissant certaines conditions expérimentales, le courant stationnaire à potentiel imposé peut être multiplié par un facteur de 1.5–1.8.

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The anodic polarisation of lead sulphide with and without a magnetic field has been studied in hydrochloric acid medium, 1 mol dm^–3, at ambient temperature. The anodic current is sensitive to the presence of a heterogeneous magnetic field. The potentiodynamic and potentiostatic studies concerning the influence of the magnetic induction on the current show a different behaviour for different magnitudes of the field. In choosing certain experimental conditions, the stationary current at an imposed potential can be multiplied by a factor of 1.5–1.8.

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On leave from Laboratoire d'Electrochimie, Université de Reims, BP 347-51062 Reims Cédex, France. Visiting Professor at l'Université Laval in 1981.     

An HF bi-phase shift keying radar: application to ice sounding inWestern Alps and Spitsbergen glaciers

A low-frequency ground penetrating radar, developed for martian subsurface sounding (Mars 96 Mission) is presented. During the preliminary campaigns, its performances have been studied by ice thickness determination on various glaciers. This radar is a pulse-compression system designed in order to limit the necessary peak power. It involves the phase modulation of the transmitted pulse by coded sequences. By moving the radar along a profile on the surface, a continuous section of the reflected energy associated with dielectric permittivity contrasts is obtained. Modulating the transmitted pulse and matched filtering the received signal provide a significant depth penetration while preserving a satisfactory range resolution. This processing is efficient even if the echo is partially shortened or if the signal is modified by differential attenuation. A multichannel filtering based on the spectral properties of the signal is then applied to the section. Experimental results of ice sounding on glaciers show that the ice-bedrock interface can be identified at depths between 30 and 120 m