No abstract available

No abstract available

[en] In phosphate processing, radium and its decay products are the naturally occurring radioactive materials that are encountered. The radium is present in the original phosphate rock, and passes through without change into the phosphogypsum, which is a by-product of the phosphoric acid industry that is obtained by reacting phosphate rock with sulphuric acid. Because of the weight of sulfuric acid added to the rock to extract the phosphate, the amount of NORM per kilogram of gypsum is less than the amount per kilogram of phosphate rock. In way to contribute for the relative regulation of the handling and use of phosphogypsum as basic input, the determination of the concentration of natural radionuclides was made, as well as the determination of the exhalation rate of ²²²Rn in samples containing different proportions of materials used in the construction industry of Brazil. The work methodology was elaborated based in the needs for a characterization of phosphogypsum. The evaluations of the physical and chemical properties of phosphogypsum were performed through thermal analyses (DTA and TGA); X-rays Fluorescence (XRF) and X-rays Diffraction (XRD). Additional analyses were carried out in order to measure natural radioactivity concentration in different types of samples, as well as the radon exhalation rate. The results showed that the phosphogypsum presents the largest values of concentrations of radionuclides associated to the natural series of ²³²Th. The concentration of ²²⁶ Ra present in the samples varied from 105 to 506 Bq/kg, the ²³²Th from 103 to ²³²Bq/kg and the 40K varied from 205 to 258 Bq/kg. The exhalation rate of ²²²Rn varied from 0.223 to 0.376 Bq/m².min. The final stage of the study evaluated the estimate of the radon concentration inside a typical room with dimensions of (4x4x2.80 m). The results presented values below the reference level adopted by legislation (148 Bq/m³). (author)

[en] The structural and magnetic properties of the tetragonal 2:14:1 hard magnetic phase (Φ) were investigated in Nd₁₆Co_76-xRu_xB ₈ alloys. The results indicated that Ru substitution does not harm the formation of Φ in Co-rich alloys. An antiferromagnetic Co-Ru coupling is concluded. The cell volume initially decreases with the Ru substitution. The coercivity is enhanced and reaches a maximum at the composition where the saturation magnetization has the lowest value. The Curie temperature as well as the mean magnetic moment decrease with increasing Ru concentration. With the increase of the Ru concentration the unit-cell volume increases. A ferrimagnetic ordering is predicted at higher Ru concentrations. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] NORM stands for 'naturally occurring radioactive material', which is a material that naturally contains one or more radionuclides, mainly, uranium, thorium and potassium-40, and their radioactive decay products, such as radium and radon. An example of this material is the Phosphogypsum (PG), which results from the processing of phosphate ore into phosphoric acid for fertilizer production. In order to support regulation of the reuse of phosphogypsum as a raw material of the Brazilian civil construction industry, a characterization study was performed. The physical and chemical properties of PG and natural gypsum were determinate by evaluating the results of thermal (DTA and TG), X-ray fluorescence (XRF), X-ray diffraction (XRD) and laser granulometric analyses. The radioactivity concentration of each sample was measured by gamma spectrometry analyses. The results of thermal analyses demonstrated that phosphogypsum must be treated (initially heated in an electrical oven at 60 deg. C for 24 hours, then sieved and heated again at 160 deg. C for one hour) to obtain the same mineralogical properties of the gypsum used in the civil construction industry. The X- ray fluorescence analysis showed that PG and natural gypsum are similar with both being composed mainly of S, O, Ca, P and small quantities of trace elements (Ce, Ti, La, Sr, Zr, and Pr). The main crystalline compounds found in PG samples were gypsita (CaSO₄.2H₂O) and in natural gypsum were bassanite (CaSO₄.0.5H₂O). The concentration of Ra-226, Ra-228 and Pb-210 present in PG samples was 467 Bq/kg, 224 Bq/kg and 395 Bq/kg, respectively. The levels of radioactivity in natural gypsum samples were much lower (around 3 Bq/kg). The same behavior was observed for the uranium and thorium content. The results of all the analyses showed that phosphogypsum can be a viable substitute for gypsum, after certain, beneficial processes. (authors)

[en] The intrinsic magnetic properties of Nd₁₆Fe_76-xRu _xB₈ alloys are investigated by means of Moessbauer spectroscopy and magnetization measurements. The Moessbauer parameters derived from fitting the six sextets assigned to the six different iron sites provide information about preferential site occupation of solute atoms. The cell volume decreases with the Ru substitution for Fe and the shrinkage of the lattice is greater in the c direction than in the a direction of the tetragonal unit cell. The decrease of the spectral area for the subpatterns corresponding to k₁ and k₂ sites with the substitution indicates that the ruthenium atoms enter preferentially in these sites, whereas the Fe atoms prefer the j-sites. The behavior of the Moessbauer parameters with changes in composition indicates that the ruthenium interactions have long range order character in this compound

[en] The magnetic properties of disordered Fe₈₆Mn_14-yCu_y alloys were investigated with several experimental techniques. The results of X-ray diffraction showed that these alloys are single phase with the A2 (BCC) structure. These are ferromagnetic alloys at room temperature, and the Curie temperature decreases with the increase of the Cu content. An abrupt loss of magnetization was observed below T_C at a temperature which increases with the reduction of the Mn content in the alloys. The addition of manganese enhances the solubility of copper in iron matrix and retains the BCC structure in iron-rich alloys. The behavior of the magnetization with temperature and its composition dependence indicate that an antiferromagnetic coupling is expected between the Fe and Mn atoms. The magnetic moments of both Fe and Mn atoms are expected to vary strongly with composition in these alloys

[en] In this work we study the structural and magnetic properties of Fe_2.5-xV_1+xAl_0.5 alloys. These compounds exhibit a ferromagnetic behavior in the ordered L2₁ phase (X₂YZ) at low temperature. The increase of the V concentration is detrimental to the onset of a long range ferromagnetic ordering in this system. The results indicate that the Fe atoms are carrying the largest magnetic moment. A re-entrant transition from a spin-glass to a ferromagnetic state was observed at low temperature

[en] Highlights: • The presence of lignin in polyurethane foams increased oil sorption capacity. • The presence of lignin resulted in a decrease in the hydrophobicity of the foams. • Langmuir isotherm predicted a maximum oil adsorption of 28.9 g g"−"1 by the PUF-10. • ΔG° (−4.4 kJ mol"−"1) indicated that adsorption process by PUF-10 was spontaneous. • The recyclability of the foam showed efficiency greater than 95% after five cycles. - Abstract: The present study describes the influence of the concentration of lignin when used as a filler in polyurethane foam for crude oil sorption. The foams (lignin 0–20 wt%) were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis, contact angle and density. The FTIR analysis confirmed urethane linkage formation, showing that the chemical structure of the polymer was preserved, despite the addition of different lignin concentrations. Thermogravimetric analysis showed that the presence of lignin has altered the onset temperature (T_o_n_s_e_t) of the foams, decreasing as the concentration of lignin is increased. The contact angle analysis showed a decrease in the hydrophobicity of the foams with increasing lignin concentration. All modified foams showed an improvement in the oil sorption capacity in a PUF/oil/water system, and the PUF-10 showed an improvement of about 35.5% compared to the PUF-blank. The Langmuir isotherm showed a better fit to the data and predicted a maximum oil adsorption of 28.9 g g"−"1 by the PUF-10. The ΔG° value of −4.4 kJ mol"−"1 indicated that crude oil adsorption process by PUF-10 was spontaneous. The results of reuse of the PUF-10 showed that oil removal efficiency remained greater than 95% after five consecutive cycles.

[en] The Fe_2+xMn_1-xAl alloys were studied experimentally to assess the effect of variations of composition around stoichiometric on the structural and magnetic properties of this system. The results indicate that the ordered L2₁(X₂YZ) structure of full Heusler alloys can be stabilized with small deviations of composition from the stoichiometric 2:1:1. The saturation magnetization is strongly composition dependent and decreases with the increase of the Mn concentration, in spite of the fact that the Mn atoms carry the largest moment in the ordered phase. The highest Curie temperature was observed for the Fe-richer alloy. Magnetic measurements suggest that atomic disorder and competition of the antiferromagnetic Fe-Mn and Mn-Mn interactions with the ferromagnetic Fe-Fe, Mn-Mn and Fe-Mn interactions lead to a frustrated couplings ending in a reentrant spin-glass behavior at low temperature