Desenvolvimento de componentes nanométricos para aplicação em células a combustível à base de sólidos estruturados e filmes finos

The present work aims the preparation of filmes of strontium-doped lanthanum manganite (perovskita) yttria-stabilized zirconia (LSM-SDC) films deposited on substrate of YSZ by means of spin coating technique having as principal objective their application to solid oxide fuel cells of intermediate temperature. La0,8Sr0,2MnO3 and Ce0,8Sm0,2O1,9 were obtained by modified Pechini method by use of gelatin which act as polymerization agent. The powders obtained were characterized by Xray fluorescence, X ray diffraction, electronic scanning microscopy and the superficial area by BET method. The results obtained by X-ray fluorescence showed that the route adopted for obtention of powders was effective in the obtention of the compositions with close values to the stoichiometrics. Ethyl cellulose was used as pore-forming agent and mixed with the LSM-SDC powders in weight proportions of 1:24, 2:23 and 1:9. The films were sintered at 1150 °C for 4 h and characterized by X-ray diffraction and scanning electron microscopy technique (SEM) and atomic force. The phases quantification of the precursory powders and of the obtained films was carried through Rietveld method. According with the analysis of SEM, as the content of ethyl cellulose was increased, the pore distribution in films become more uniform and the pore size reduced. The methodology used for the obtention of the films was very efficient, considering a material was obtained with characteristics that were proper to the application as electrolyte/cathode system to solid oxide fuel cells

efeito da aplicação de uma solução salina no crescimento e na composição química da atriplex nummularia

This study aimed to analyze the effect of a saline solution on growth and chemical composition of Atriplex nummularia, shrubby plant, absorbing salts used in the diet of animals and the management of water and saline soils. These plant seedlings were planted and grown in a reserved area at the Federal University of Rio Grande do Norte. The plantation was divided into two blocks, in which one of them was irrigated with saline solution with a concentration of 2840 mgL-1 of NaCl and the second group was irrigated with drinking water. After six months, the plants were collected, harvested and divided into three parts: leaf, thin and thick stem. Monthly, dimension measurements were carried out for cataloging the growth of Atriplex. Ion Chromatography (IC) and Optical Emission Spectroscopy Inductively Coupled Plasma (ICP-OES) were used to analyze the chemical composition of the partition plant parts. The results of these analyses revealed that an absorption process of anions and cations by Atriplex nummularia plant during its growth was achieved, in particular by a higher concentration of sodium and chloride ions. Scanning electron microscopy images showed and confirmed the presence of small crystals on the leaf surface. Electrical conductivity and pH measurements of the aerial parts of the plant were carried out and these results showed that the leaf is the plant part where there is a largest concentration of ions. In addition, measurements of specific surface were obtained from irrigated plants with saline solution, achieving higher surface area, in all cases. Plant dimensions obtained monthly showed that the plants irrigated with water grew 5% more than those plants irrigated with saline solution. Based on results obtained, Atriplex plant showed a higher potential to survive and adapt to environments (aquatic or geological) with high levels of salinity and this property can be used as a tool for removing salts/metals from industrial contaminated soils and effluents.

Obtenção de biodiesel através da transesterificação do óleo de farelo de arroz utilizando KI/Al2O3

This study proposes to find a biodiesel through transesterification of rice bran oil with KI/Al2O3 checking the influence of two types of alumina (Amorphous and Crystalline) for conversion into methyl esters. The catalyst was synthesized by the wet impregnation method. Adding 30 mL of 35% KI(aq.) in 10 g of alumina, under stirring at 80 °C for 3 hours. The reaction conditions used in this study were optimized, with a molar ratio methanol:oil of 15:1, 8 h of reaction time and reflux temperature. The catalyst amount was varied in the range of 1 to 5 % wt. The solid catalysts materials were analyzed by: x-ray diffraction (XRD), thermogravimetry (TG), N2 adsorption/desorption, scanning electron microscopy (SEM) and basicity, for the identification of its structure and composition, verifying the presence of basic sites. The results showed that Al2O3(A) presents an amorphous structure, high surface area and a better catalytic activity, in relation to the catalyst synthesized with Al2O3(C) support that proved to have a more crystalline structure, having as well, a lesser surface area, enabling difficulties for the incorporation of active sites. The obtained biodiesel with 5% wt. KI/Al2O3(A) presented physicochemical properties within the standards specified by the Resolution No 7/2008 ANP and obtained the best reaction yield with 95.2%, according to quantitative measurement from the TG, which showed 96.2% conversion into methyl esters. It was furthermore found that with the increasing amount of the quantity of the catalyst in the reaction, there was also an increase in the ester content obtained. The specific mass and the kinematic viscosity were reduced with the increase of the amount of quantity of the catalyst, indicating an increase in the conversion of triglycerides

Estudo termoanalítico de medicamentos de referência, genérico e similar

This study aimed to apply, thermogravimetriy /derivative Thermogravimetriy (TG/DTG), differential scanning calorimetry (DSC), Differential Thermal Analysis (DTA), to conduct a comparative study on drug reference, generic and whose active principles are similar captopril hydrochlorothiazide, ampicillin, paracetamol, aspirin and mebendazole sold in local pharmacies. Samples of the active ingredients and dosage forms were also characterized by absorption infrared spectroscopy (IR), X-ray diffraction (XRD) and microscopy scanning electron (SEM). The TG / DTG curves showed a general similarity in the thermal behavior of the samples, but also showed the influence of excipients on the thermal stability. The DSC curve of the generic base hydrochlorothiazide showed no peak on the fusion of the drug due to interference of lactose as a diluent, which causes interaction with the active principle causing their degradation before the merger. The DSC curves of the drugs consisting of paracetamol showed reproducibility at the melting point of the active and the other thermal events. The DSC result of binary mixtures involving captopril / magnesium stearate and mebendazole/magnesium stearate showed possible interactions or incompatibilities evidenced by the displacement of the melting point of both drugs. The other mixtures showed no change. The infrared spectra presented were very similar, indicating the presence of functional groups characteristic of the constituents of the samples. The X-ray diffraction showed peaks indicative of crystalline structure of the active ingredients as well as some of the ingredients in the formulation of the drug and the micrographs indicate a general heterogeneity in the size distribution of particles in the samples

Estudo da viabilização do uso da mistura híbrida ferrocarbonila / ferrita de NI0,5Zn0,5Fe2o4 como material absorvedor de radiação eletromagnética

Were synthesized ferrites of NiZn on systems Ni0,5Zn0,5Fe2O4, the precursors citrate method. The decomposition of the precursors was studied by thermogravimetric analysis and spectroscopy in the infrared region, the temperature of 350°C/3h. The evolution of the phases formed after calcinations at 350ºC/3h, 600, 1000 and 1100ºC/2h was accompanied by X-ray diffraction using the Rietveld refinement method for better identification os structures formed. Was observed for samples calcined at different temperatures increased crystallinity with increasing calcination temperature, being observed for the samples calcined at 900 and 1100 º C/2h was the precipitation of a secondary phase, the phase hematite. The ferrocarbonila of industrial origin was analyzed by X-ray diffraction and Rietveld for the identification of its structure. The carbonyl iron was added NiZn ferrite calcined at 350ºC/3h, 600, 900, 1000 and 1100ºC/2h to the formation of hybrid mixtures. They were then analyzed by Xray diffraction and Rietveld. The NiZn ferrite and ferrocarbonila as well as the hybrid mixtures were subjected to analysis of scanning electron microscopy, magnetic measurements and reflectivity. The magnetic measurements indicated that the ferrite, the ferrocarbonila, as well as hybrid mixtures showed characteristics of soft magnetic material. The addition of ferrocarbonila in all compositions showed an increase in the results of magnetic measurements and reflectivity. Best result was observed in the increase of the magnetization for the hybrid mixture of Ferrocarbonila / ferrite of NiZn calcined at 600ºC/2h. The mixture Ferrocarbonila / ferrite calcined 1000°C/2h presented better absorption of electromagnetic radiation in the microwave

Obtenção e Caracterização Físico-Química do Sistema Compósito PEG-TiO2

Hybrid systems formed from polymers and transition metals have now their physical and chemical properties extensively investigated for use in electronic devices. In this work, Titanium Dioxide (TiO2) from the precursor of titanium tetrabutoxide and the composite system Poly(Ethylene Glycol)-Titanium Dioxide (TiO2-PEG) were synthesized by sol-gel method. The PEG as acquired and TiO2 and composites powders were analyzed by X-Ray Diffraction (XRD), Spectroscopy in the Infrared region with Fourier transform (IRFT), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). In the XRD analysis were observed in the TiO2 crystal faces of one of its polymorphs - anatase phase, crystal planes in Poly (Ethylene Glycol) with considerable intensity and in the composite systems the mixture of crystal faces of their precursors isolated and reduction of crystallinity. The TG / DTG suggested increasing the thermal instability of PEG in the composite powders as TiO2 is incorporated into the system. Spectral analysis presented in the infrared overlapping bands for the polymer and metal oxide, reducing the intensity of symmetric stretching of ligand groups in the main chain polymer and angular deformations; were observed using SEM micrographs of the morphological changes suffered by composite systems with the variation of the oxide concentration. Analyses by impedance spectroscopy indicated that the increased conductivity in composite occurs in line with the addition of the metal oxide concentration in the composite system

Síntese e caracterização de carreadores de oxigênio para combustão com recirculação química obtidos via reação de combustão assistida por microondas

Perovskites oxides win importance by its properties and commercials applications, they have a high thermal stability, have conductive properties, electrical, catalytic, electro catalytic, optical and magnetic, and are thermally stable. Because of these properties, are being widely studied as carriers of oxygen in the process of power generation with CO2 capture. In this work, the base carrier system La1-xMexNiO3 (Me = Ca and Sr) were synthesized by the method via the combustion reaction assisted by microwave. were synthesized from the combustion reaction method by microwave process. This method control the synthesi`s conditions to obtain materials with specific characteristics. The carriers calcined at 800 ° C/2h were analyzed by thermal analysis (TG-DTA), to verify its thermal stability, X-ray diffraction (XRD) to verify the phase formation, with subsequent refinement by the Rietveld method, to quantify the percentage of phases formed, the surface area by BET method was determined, scanning electron microscopy (SEM) was obtained to evaluate the material morphology and temperature programmed reduction (TPR) was done to observe the metallic phase of the nickel. After all proposed characterization and analysis of their results can be inferred to these oxides, key features so that they can be applied as carriers for combustion reactions in chemical cycles. The final products showed perovskite-type structures K2NiF4 (main) and ABO3.

Dessulfurização oxidativa em diesel utilizando catalisadores à base de vanádio ou manganês

The oxidative desulfurization process (ODS) of a commercial diesel fuel was performed under mild conditions in the presence of catalysts based on vanadium or manganese, supported on alumina, clays (commercial, natural and pillared) and zeolites (NaX, NaY, beta, mordenite and ZSM-5). The catalysts were synthesized by wet impregnation and characterized by X-ray diffraction, textural analysis by N2 adsorption and scanning electron microscopy. The dibenzothiophene (DBT) was used as sulfur compound in catalytic evaluation. The reactions were performed using acetonitrile as solvent and the hydrogen peroxide as oxidant at 55°C. The reaction products were analized by gas chromatography (GC-FID). In the studied conditions, the process was efficient due to the DBT was converted to its corresponding sulfone. Both DBT and corresponding sulfone were extracted by the solvent. Removals and oxidations up to 100% of sulfur compound were achieved. The catalysts supported on ZSM-5 zeolite showed are more effective for oxidation reaction of sulfur compound, presenting the best results. It was observed for oxidation reaction, that vanadium catalysts were more effective and manganese catalysts showed best results for removal of sulfur compounds

Estudo de titanatos nanoestruturados obtidos por tratamento hidrotérmico de óxido de titânio em meio alcalino

TiTanate NanoTubes (TTNT) were synthesized by hydrothermal alkali treatment of TiO2 anatase followed by repeated washings with distinct degrees of proton exchange. TTNT samples with different sodium contents were characterized, as synthesized and after heattreatment (200-800ºC), by X-ray diffraction, scanning and transmission electron microscopy, electron diffraction, thermal analysis, nitrogen adsorption and spectroscopic techniques like FTIR and UV-Vis diffuse reflectance. It was demonstrated that TTNTs consist of trititanate structure with general formula NaxH2−xTi3O7·nH2O, retaining interlayer water in its multiwalled structure. The removal of sodium reduces the amount of water and contracts the interlayer space leading, combined with other factors, to increased specific surface area and mesopore volume. TTNTs are mesoporous materials with two main contributions: pores smaller than 10 nm due to the inner volume of nanotubes and larger pores within 5-60 nm attributed to the interparticles space. Chemical composition and crystal structure of TTNTs do not depend on the average crystal size of the precursor TiO2-anatase, but this parameter affects significantly the morphology and textural properties of the nanostructured product. Such dependence has been rationalized using a dissolution-recrystallization mechanism, which takes into account the dissolution rate of the starting anatase and its influence on the relative rates of growth and curving of intermediate nanosheets. The thermal stability of TTNT is defined by the sodium content and in a lower extent by the crystallinity of the starting anatase. It has been demonstrated that after losing interlayer water within the range 100-200ºC, TTNT transforms, at least partially, into an intermediate hexatitanate NaxH2−xTi6O13 still retaining the nanotubular morphology. Further thermal transformation of the nanostructured tri- and hexatitanates occurs at higher or lower temperature and follows different routes depending on the sodium content in the structure. At high sodium load (water washed samples) they sinter and grow towards bigger crystals of Na2Ti3O7 and Na2Ti6O13 in the form of rods and ribbons. In contrast, protonated TTNTs evolve to nanotubes of TiO2(B), which easily convert to anatase nanorods above 400ºC. Besides hydroxyls and Lewis acidity typical of titanium oxides, TTNTs show a small contribution of protonic acidity capable of coordinating with pyridine at 150ºC, which is lost after calcination and conversion into anatase. The isoeletric point of TTNTs was measured within the range 2.5-4.0, indicating behavior of a weak acid. Despite displaying semiconductor characteristics exhibiting typical absorption in the UV-Vis spectrum with estimated bandgap energy slightly higher than that of its TiO2 precursor, TTNTs showed very low performance in the photocatalytic degradation of cationic and anionic dyes. It was concluded that the basic reason resides in its layered titanate structure, which in comparison with the TiO2 form would be more prone to the so undesired electron-hole pair recombination, thus inhibiting the photooxidation reactions. After calcination of the protonated TTNT into anatase nanorods, the photocatalytic activity improved but not to the same level as that exhibited by its precursor anatase

Estudo das ligas titânio-zircônio resultantes do processo de fundição plasma-skull para aplicações como biomateriais

The aim of this work was to study a series of 11 different compositions of Ti-Zr binary alloys resistance to aggressive environment, i. e., their ability to keep their surface properties and mass when exposed to them as a way to evaluate their performance as biomaterials. The first stage was devoted to the fabrication of tablets from these alloys by Plasma-Skull casting method using a Discovery Plasma machine from EDG Equipamentos, Brazil. In a second stage, the chemical composition of each produced tablet was verified. In a third stage, the specimen were submitted to: as-cast microstructure analysis via optical and scanning electron microscopy (OM and SEM), x-ray dispersive system (EDS) chemical analysis via SEM, Vickers hardness tests for mechanical evaluation and corrosion resistence tests in a 0.9% NaCl solution to simulate exposition to human saliva monitored by open circuit potential and polarization curves. From the obtained results, it was possible to infer that specimens A1 (94,07 wt% Ti and 5,93% wt% Zr), A4 (77,81 wt % Ti and 22,19 wt % Zr) and A8 (27,83 wt% Ti and 72,17 wt% Zr), presented best performance regarding to corrosion resistance, homogeneity and hardness which are necessary issues for biomaterials to be applied as orthopedic and odontological prosthesis

Membranas de quitosana micro e macroporosas : preparo, caracterização e estudos de permeabilidade

Two methodologies were proposed to obtain micro and macroporous chitosan membranes, using two different porogenic agents. The methodologies proved to be effective in control the porosity as well as the pore size. Thus, microporous membranes were obtained through the physical blend of chitosan and polyethylene oxide (PEO) on an 80:20 (m/m) ratio, respectively, followed by the partial PEO solubilization in water at 80 ◦C. Macroporous chitosan membranes with asymmetric morphology were obtained using SiO2 as the porogenic agent. In this case, chiotsan-silica ratios used were 1:1, 1:3 and 1:5 (m/m). Membranes characterization were carried out by SEM (scanning electronic microscopy), X-ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), Thermal analysis (TG, DTG , DSC and DMTA). Permeability studies were performed using two model drugs: sodium sulfamerazine and sulfametoxipyridazine. By transmission FTIR it was possible to confirm the complete removal of SiO2. The SEM images confirmed the porous formation for both micro and macroporous membranes and also determined their respective sizes. By thermal analysis it was possible to show differences related with water sorption capacity as well as thermal stability for both membranes. DTG and DSC allowed evidencing the PEO presence on microporous membranes. The absorbance x time curves obtained on permeability tests for micro and macroporous membranes showed a linear behavior for both drugs in all range of concentration used. It was also observed, through P versus C curves, an increase in permeability of macroporous membranes according to the increase in porosity and also a decrease on P with increase in drug concentration. The influences of the drug molecular structure, as well as test temperatures were also evaluated

Síntese e caracterização de membranas zeolíticas tipo mfi e aplicação em separação de aromáticos

The synthesis of MFI-type zeolite membranes was carried by the process in situ or hydrothermal crystallization. We studied the homogenization time of the room temperature and gel filtration just before the crystallization step performed out in an oven, thus obtaining a more uniform zeolite film. The powder synthesized zeolite (structure type MFI, Silicalite) was characterized by several complementary techniques such as Xray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis, temperature programmed desorption (TPD), Fourier Transform infrared spectroscopy (FTIR) and textural analysis by nitrogen adsorption (specific surface area). For the purpose of evaluating the quality of the layer supported on the ceramic support, N2 permeation tests were carried starting from room temperature to 600 °C, where values were observed values more appropriate permeation from 200 °C. With the data obtained, it was made into a graph of temperature versus permeation function, the curve of surface diffusion was found. For scanning electron microscopy, we observed the formation of homogeneous crystals and the zeolite film showed no fissures or cracks, indicating that the process of synthesis and subsequent treatments not damaged the zeolite layer on the support. Carried permeation studies were found values ranging from 3.64x10-6 to 3.78x10-6, 4.71x10-6 to 5.02x10-6, to pressures 20 and 25 psi, respectively. And the mixture xylenes/N2 values were between 5.39x10-6 to 5.67x10-6 and 8.13x10-6 to 8.36x10-6, also for pressures of 20 and 25 psi. The values found for the separation factor were 15.22 at 400 °C in the first experiment and 1.64 for the second experiment at a temperature of 150 °C. It is concluded that the Silicalite membrane was successfully synthesized and that it is effective in the separation of binary mixtures of xylenes

Matrizes poliméricas puras e modificadas para adsorção do gás sulfeto de hidrogênio

The underground natural gas found associated or not with oil is characterized by a mixture of hydrocarbons and residual components such as carbon dioxide (CO2), nitrogen gas (N2) and hydrogen sulfide (H2S), called contaminants. The H2S especially promotes itself as a contaminant of natural gas to be associated with corrosion of pipelines, to human toxicity and final applications of Natural Gas (NG). The sulfur present in the GN must be fully or partially removed in order to meet the market specifications, security, transport or further processing. There are distinct and varied methods of desulfurization of natural gas processing units used in Natural Gas (UPGN). In order to solve these problems have for example the caustic washing, absorption, the use of membranes and adsorption processes is costly and great expenditure of energy. Arises on such findings, the need for research to active processes of economic feasibility and efficiency. This work promoted the study of the adsorption of sulfide gas in polymer matrices hydrogen pure and modified. The substrates of Poly(vinyl chloride) (PVC), poly(methyl methacrylate) (PMMA) and sodium alginate (NaALG) were coated with vanadyl phosphate compounds (VOPO4.2H2O), vanadium pentoxide (V2O5), rhodamine B (C28H31N2O3Cl) and ions Co2+ and Cu2+, aiming to the adsorption of hydrogen sulfide gas (H2S). The adsorption tests were through a continuous flow of H2S in a column system (fixed bed reactor) adsorption on a laboratory scale. The techniques used to characterize the adsorbents were Infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), X-ray fluorescence (XRF), the X-ray diffraction (XRD) electron microscopy (SEM). Such work indicates, the results obtained, the adsorbents modified PMMA, PVC and NaALG have a significant adsorptive capacity. The matrix that stood out and had the best adsorption capacity, was to ALG modified Co2+ with a score of 12.79 mg H2S / g matrix

Hidrofobização, caracterização e aplicação da vermiculita para remoção de óleo insolúvel em água

Among the various layered silicates, vermiculite has been used as one of the adsorbent material by presenting the ion exchange capacity which facilitates the removal of organic compounds which are potential pollutants in relation to the water surface. The importance of the modification of clay minerals by hydrophobization with carnauba wax establishes the increase in oil removal capacity in aqueous medium, it contributes to a better environment for life in ecosystems. The vermiculite when expanded decreases its hydrophobicity requiring the use of a hydrophobizing leaving - the organoclay. In this work were used in the process of modifying the particle sizes of vermiculite -18+16, -16 +20 and -20 +35 #. Samples of vermiculite hydrophobized with carnauba wax and clay mineral without hydrophobizing were characterized with physicochemical analyzes and analytical. Techniques were used: thermal analysis (thermogravimetry and derivative thermogravimetry), infrared spectroscopy, scanning electron microscopy, fluorescence rays - x adsorption tests. The TG / DTG was used to evaluate the thermal behavior of expanded vermiculite and carnauba wax and samples hidrofobizadas with percentages of 5, 10 and 15 % by weight of hydrophobizing. The results of FTIR confirmed increase of the characteristic signs of carnauba wax in samples hidrofobizadas as the greatest amount of hydrophobizing the clay mineral used in hydrophobization. Thermogravimetry and FTIR show based on the results that coating the surface of the vermiculite occur homogeneously. The data obtained by the technique of x-ray fluorescence with loss on ignition confirmed the results of thermogravimetric analysis in relation to the percentage of wax incorporated. The fluorescence indicates through information provided by the analysis shows that the material covered - is homogeneous. The mev inspection was used to texture and morphology of the clay mineral with and without carnauba wax. The scanning electron microscopy confirms the deposition of wax evenly over the surface of the mineral as indicated by the other techniques. To verify the adsorption capacity of the clay without hydrophobizing hydrophobized and used a fixed volume of water to 1 ½ liters in each experiment with 3 g to 50 g of oil sample. The results show that better extraction of oil for the material processed corresponds to 260 % relative to the weight of the sample coated and greater than 80 % of the oil drop in the system

Estudo das características magnéticas e absorvedoras das ferritas de nizn, niznmn, mnzn, nimg, nicuzn e nicuznmg obtidas via método do citrato precursor

Were synthesized systems Ni0,5Zn0,5Fe2O4, i0,2Zn0,5Mn0,3Fe2O4, Mn0,5Zn0,5Fe2O4, Ni0,5Mg0,5Fe2O4, Ni0,2Cu0,3Zn0,5Fe2O4 and Ni0,2Cu0,3Zn0,5Mg0,08Fe2O4, the precursors citrate method. The decomposition of the precursors was studied by thermogravimetric analysis and spectroscopy in the infrared region, the temperature of 350°C/3h. The evolution of the phases formed after calcinations at 350, 500, 900 and 1100ºC/3h was accompanied by X-ray diffraction using the Rietveld refinement to better identify the structures formed. The materials were also analyzed by scanning electron microscopy, magnetic measurements and analysis of the reflectivity of the material. The samples calcined at different temperatures showed an increase of crystallinity with increasing calcination temperature, verifying that for some compositions at temperatures above 500°C precipitates of second phase such as hematite and CuO. The compositions of manganese present in the structure diffusion processes slower due to the ionic radius of manganese is greater than for other ions substitutes, a fact that delays the stabilization of spinel structure and promotes the precipitation of second phase. The compositions presented with copper precipitation CuO phase at a temperature of 900 and 1100ºC/3h This occurs according to the literature because the concentration of copper in the structure is greater than 0.25 mol%. The magnetic measurements revealed features of a soft ferrimagnetic material, resulting in better magnetic properties for the NiZn ferrite and NiCuZnMg at high temperatures. The reflectivity measurements showed greater absorption of electromagnetic radiation in the microwave band for the samples calcined at 1100ºC/3h, which has higher crystallite size and consequently the formation of multi-domain, increasing the magnetization of the material. The results of absorption agreed with the magnetic measurements, indicating among the ferrites studied, those of NiZn and NiCuZnMg as better absorbing the incident radiation.