Temperature dependence of core loss in cobalt substituted Ni-Zn-Cu ferrites

The temperature dependence of core loss in cobalt substituted Ni-Zn-Cu ferrites was investigated. Co2+ ions are known to lead to a compensation of the magneto-crystalline anisotropy in Ni-Zn ferrites, at a temperature depending on the cobalt content and the Ni/Zn ratio. We observed similar behaviour in Ni-Zn-Cu and it was found that the core loss goes through a minimum around this magneto-crystalline anisotropy compensation. Moreover, the anisotropy induced by the cobalt allowed a strong decrease of core loss, a ferrite having a core loss of 350 mW/cm3 at 80 ^\circ C was then developed (measured at 1.5 MHz and 25 mT). This result represents an improvement of a factor 4 compared to the state of art Ni-Zn ferrites

X-ray photoelectron spectroscopy and friction studies of nickel-zinc and manganese-zinc ferrites in contact with metals

X-ray photoelectron spectroscopy analysis and sliding friction experiments were conducted with hot-pressed, polycrystalline Ni-Zn and Mn-Zn ferrites in sliding contact with various transition metals at room temperature in a vacuum of 30 nPa. The results indicate that the coefficients of friction for Ni-Zn and Mn-Zn ferrites in contact with metals are related to the relative chemical activity in these metals: the more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites correlate with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite surfaces increases the coefficients of friction for the Ni-Zn and Mn-Zn ferrite-metal interfaces

Development of battery separator composites

Improved inorganic-organic separators developed by NASA were commercially prepared. A single-ply asbestos substrate was developed, as well as alternative substrates based on cellulose and on polypropylene fibers. The single-ply asbestos was bound with butyl rubber and was functionally superior to the formerly used polyphenylene oxide saturated sheet. Commercially prepared separators exhibited better measured separator properties than the NASA standard. Cycle life in Ni/Zn and Ag/Zn cells was related to substrate, decreasing in the order; asbestos cellulose paper nonwoven polypropylene. The cycle life of solvent-coated separators was better than aqueous in Ni/Zn cells, while aqueous coatings were better in Ag/Zn cells

Geofractionation of heavy metals and application of indices for pollution prediction in paddy field soil of Tumpat, Malaysia

The present study investigates the concentration of Pb, Cd, Ni, Zn, and Cu in the paddy field soils collected from Tumpat, Kelantan. Soil samples were treated with sequential extraction to distinguish the anthropogenic and lithogenic origin of Pb, Cd, Ni, Zn, and Cu. ELFE and oxidizable-organic fractions were detected as the lowest accumulation of Pb, Cd, Ni, Zn, and Cu. Therefore, all the heavy metals examined were concentrated, particularly in resistant fraction, indicating that those heavy metals occurred and accumulated in an unavailable form. The utilization of agrochemical fertilizers and pesticides might not elevate the levels of heavy metals in the paddy field soils. In comparison, the enrichment factor and geoaccumulation index for Pb, Cd, Ni, Zn, and Cu suggest that these heavy metals have the potential to cause environmental risk, although they present abundance in resistant fraction. Therefore, a complete study should be conducted based on the paddy cycle, which in turn could provide a clear picture of heavy metals distribution in the paddy field soils

Sintered silicon carbide molded body and method for its production

Sintered silicon carbide shapes are described. They are produced by using a composition containing an oxide of at least one element chosen from the group: Li, Be, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Nb, Mo, Ba, Tc, Ta, W and Th as a supplement to known sintering aids

Termodinamika adsorpcije n-heksana na jonski izmenjenim X zeolitima

In this work, the free energy changes and entropy changes of adsorption of n-hexane on zeolites of the MxNa87-2xX (M=Co,Ni,Zn,Cd) type were determined using their isosteric sorption heats. It was found that the exchange of Na ions in NaX with bivalent cations (Co, Ni, Zn, Cd) significantly alters the adsorption characteristics of NaX zeolite. The free energy changes and entropy changes of n-hexane adsorption were dependent on the surface coverage and on the nature of the charge-balancing cation. The specific influence of the exchanged cations on the free energy changes and entropy changes of sorption of n-hexane originates from the size, location and electronic configuration of the cation.U ovom radu su određene promene slobodne energije i promena entropije adsorpcije n-heksana na zeolitima tipa MxNa87-2xX (M=Co,Ni,Zn,Cd) na osnovu izosternih toplota sorpcije. Pokazano je da izmena Na+ jona u NaX zeolitu dvovalentnim katjonima (Co,Ni,Zn,Cd) značajno menja adsorpcione karakteristike NaX zeolita. Takođe je utvrđeno da promena slobodne energije i promena entropije adsorpcije n-heksana zavisi i od stepena pokrivenosti površine zeolita

Microstructural and Dielectric Properties of Ni-Zn and Li-Ni-Zn Ferrites by Impedance Spectroscopy.

The real and imaginary parts of the complex impedances and the loss angle (8) of iO.5Zn05Fe20, and (Lioleo.5)O.5Nio.2ZnO.3 Fe20, ferrites were measured at 300 K in the frequency range of 1 - 10 MHz using a frequency response analyser. The complex - plane impedance spectra of the samples are associated with equivalent circuits composed of resistive and capacitive elements due to the bulk (grain) and the grain boundary components. The measured and simulated impedances were analysed using the complex nonlinear least square (CNLS) fitting method. The simulated components of the circuit are interpreted as the characteristic parameters of the microstructural properties of the materials. Microstructural properties are complemented by a morphological study using a scanning electron microscope. The dielectric properties at low and high frequency regimes are interpreted as mainly due to the interfacial and orientational polarizations respectively. A region of negative capacitances at low frequencies is observed for both samples. Frequency dependence of the characteristic parameters of the microstructural components and the dielectric behaviour of the materials are discussed