Temperature dependence of the resistivity and tunneling magnetoresistance of sputtered FeHf(Si)O cermet films

We have studied the tunneling resistivity and magnetoresistance of reactive sputter deposited FeHfO and FeHfSiO thin granular films. Maximum magnetoresistance ratios at room temperature of 2% and 3.2% were observed for films with compositions of Fe47Hf10O43 and Fe40Hf6Si6O48, respectively. The magnetoresistance shows a decrease with temperature, which cannot be explained by spin-dependent tunneling only. We propose that spin-flip scattering in the amorphous FeHf(Si)O matrix causes this decrease as function of temperature. A two current model for the tunnel magnetoresistance, taking into account spin-flip scattering, is presented which can describe the observed temperature dependence of the magnetoresistance

On the frequency dependence of the magnetic permeability of FeHfO thin films

The frequency dependence of the magnetic permeability as well as of the electrical impedance have been investigated for soft-magnetic granular FeHfO thin films. The impedance measurements indicate that capacitive effects resulting from the inhomogeneous structure of the layers are of no importance for the roll off of the permeability of the present films. The frequency behavior at various FeHfO thicknesses shows that eddy current effects start to play a role above thicknesses of 10 µm. Below this thickness ferromagnetic resonance dominates the roll off

Phosphate recycling in the phosphorus industry

The article describes the potential and limitations for recovery of phosphate from secondary materials in the production process for white phosphorus. This thermal process involves the feeding of phosphate rock, cokes and pebbles to a furnace. The reducing conditions in the furnace promote the formation of white phosphorus. The article describes the limitations of feeding secondary phosphate sources to the process in terms of the amount of phosphate present, impurities present, water content, etc. It then explains possibility of phosphate recovery from different sources like sewage sludge, manure, bone meal ash, industrial and food industry waste streams. It states that waste legislation in different countries restricts the possibility of obtaining secondary phosphates from wastes and a less rigid legislation and regulation would help in obtaining waste as sources for phosphate recovery

Remediation of fine fractions of dredged sediments by flotation

In the Netherlands, large quantities of contaminated dredged sludge have to be deposited or treated in the near future. Because of the large amounts of small particles involved, successful treatment is difficult. In this study a new flotation method on laboratory scale was used as an alternative remediation technique. Dissolved air was used to create small bubbles. Tests were performed with the finest fractions of sediments of Overschie (Rotterdam) and Petrol Harbor (Amsterdam) sludges contaminated with Polycyclic Aromatic Hydrocarbons (PAH). Several agents and conditions were tested with respect to the flotation efficiency. For Overschie sludge the best results were obtained without collector and SDS as frother. The PAH concentration in the Froth was up to 8 times higher than that in the non-floating fractions. The collected amount of dry matter in the froth was around 13ÐWith a two step flotation, the PAH concentration of the non-floating "clean" fraction was reduced from 240 mg (kg d m(-1)) to 99 mg (kg d m(-1)). For Petrol Harbor sludge the best results were obtained with the alcohol-based frothers Aerofroth and Montanol. The flotation was less selective than with Overschie sediment. Around 50Ðsolids were collected in the froth and the PAH concentration in the Froth was around 2 times higher than in the Settled fraction and 3-5 times higher than in the fraction Remains