Dynamic mechanical properties of hybrid magnetic composite materials with polymer matrix

Savremena istraživanja u oblasti razvoja magnetnih kompozitnih materijala na bazi Nd-Fe-B legura usmerena su u tri osnovna pravca: povećanje magnetne energije, odnosno optimizacija magnetnih svojstava, poboljšanje otpornosti na koroziju i redukovanje sadržaja retke zemlje (Nd), u cilju sniženja cene finalnog magnetnog materijala, uz zadržavanje visokih vrednosti maksimalne magnetne energije. Razvoj nanokristalnih i nanokompozitnih magnetnih legura tipa Nd-Fe-B znatno je povećao interesovanje za istraživanje i razvoj magnetnih kompozitnih materijala sa polimernom matricom tzv. bonded magneta, jer su se ovi magnetni prahovi pokazali kao izuzetno pogodni za njihovu proizvodnju. Primenom različitih procesnih tehnika u procesu proizvodnje bonded magneta data je mogućnost upotrebe različitih magnetnih prahova u kombinaciji sa različitim polimernim materijalima kao vezivnim sredstvima. Razvoj bonded tehnologije, istraživanje mogućnosti primene različitih vrsta i udela magnetnih prahova i polimernih veziva, ispitivanje njihovog uticaja, kao i uticaja procesnih parametara, na postizanje optimalnih mehaničkih i magnetnih svojstava kompozita je u istraživačkom fokusu u poslednjih nekoliko godina. Istraživački trend se ogleda u razvoju bonded hibridnih magnetnih kompozitnih materijala sa poboljšanim dinamičko-mehaničkim svojstvima i znatno nižom cenom zbog supstitucije skupih Nd-Fe-B magnetnih prahova jeftinijim feritnim magnetnim prahovima, uz postizanje zadovoljavajućih vrednosti maksimalne magnetne energije. Iz analize i obrade literaturnih podataka može se konstatovati da je, u do sada publikovanim radovima, uticaj kritičnih parametara na finalna svojstva magnetnih kompozitnih materijala ovog tipa analiziran ograničeno i pojedinačno. Na osnovu detaljne obrade raspoloživih literaturnih podataka se može zaključiti da još uvek nije postignuto optimalno rešenje odnosa: struktura – dinamičko-mehanička svojstva – magnetna svojstva – cena bonded magneta. Predmet ove doktorske disertacije je teorijsko i eksperimentalno izučavanje uticaja, vrste i udela magnetnog praha, tipa i udela polimernog veziva, kao i procesnih parametara u primenjenim metodama sinteze, na strukturna, dinamičko-mehanička svojstva u funkciji temperature, mehanička svojstva na sobnoj temperaturi i magnetna svojstva istraživanih magnetnih kompozitnih materijala. Istraživanje mogućnosti poboljšanja fizičkih svojstava bonded magneta je obuhvaćeno istraživačkim ciljem ove disertacije i realizovano je u eksperimentalnom delu, kroz sintezu i karakterizaciju hibridnih magnetnih kompozitnih materijala dobijenih mešanjem dva ili više magnetnih prahova. Interakcije između različitih magnetnih komponenti, kao i interakcije između magnetnih komponenti i polimerne matrice razmatrane su u korelaciji sa dinamičko-mehaničkim i magnetnim svojstvima sintetizovanih magnetnih kompozita...Current research efforts in the field of magnetic composite materials based on Nd-Fe-B alloys are directed towards three main goals: increase of magnetic energy and optimization of magnetic properties, improvement of corrosion resistance and reduction of rare-earth element (Nd) content as a way of the price reduction of the final magnetic material but with retained magnetic energy. Development of Nd-Fe-B nanocrystalline and nanocomposite magnetic alloys has significantly increased interest in research and development of composite magnetic materials with polymer matrix i.e. bonded magnets, since powders of these alloys are proved to be very suitable for their production. Application of different processing techniques in the production process of bonded magnets has provided the opportunity for utilization of different magnetic powders combined with variety of polymer binders. Improvement of production technology of bonded magnets, research of possibilities of application of different types and contents of magnetic powders and polymer binders and investigation of the influence of process parameters on obtaining of optimal mechanical and magnetic properties of the magnetic composite materials are in research focus over the past few years. The research trend is aimed at development of bonded hybrid magnetic composite materials with improved dynamic mechanical properties and significantly lower price due to substitution of expensive Nd-Fe-B magnetic powders with cheaper ferrite magnetic powders, but with suitable values of magnetic energy. Analysis of literature data revealed limited and individual studies of the influence of critical parameters on final properties of magnetic composite materials of this type. Based on more detail analysis of literature data it could be concluded that still there are no optimal solutions of relation: structure – dynamic mechanical properties – magnetic properties – price of boned magnet. The scope of this thesis is theoretical and experimental investigation of the influence of type and content of magnetic powder, type and content of polymer binder and process parameters in the applied methods of synthesis on the structural and dynamic mechanical properties of the investigated magnetic composite materials in the function of temperature as well as mechanical and magnetic properties at ambient temperature. Investigation of possible improvement of physical properties of the bonded magnets was included in the goal of this thesis and it was realized in the experimental part through synthesis and characterization of hybrid magnetic composite materials produced by mixing of two or more magnetic powders..

An overstoichiometric Nd–Fe–B hard magnetic material

A commercial Nd-rich Nd–Fe–B-based hard magnetic material was studied. The obtained results were compared before and after recording of the thermomagnetic curve up to 800 °C. The curve itself showed clearly besides Curie points of the Nd2Fe14B phase and α-Fe also another critical temperature. Mössbauer spectroscopic (MS) phase analysis and X-ray diffraction analysis (XRD) showed in addition to the commonly known phases Nd2Fe14B and NdFe4B4 also some paramagnetic and ferromagnetic iron atoms (MS) and Fe17Nd2 intermetallics (XRD). During the exerted thermal treatment, the content of the Nd2Fe14B and NdFe4B4 phases remained almost unchanged, while iron atoms from remnant minor phases built a separate α-Fe phase. The XRD pattern also showed the presence of some minor Nd phase. The results of Squid magnetic measurements suggest a nanocrystalline decoupled structure of the Nd-rich alloy in the optimized magnetic state. Measurement of the magnetization loop showed, in spite of small changes in the phase composition, that magnetic properties of the quality material deteriorated during the thermal treatment

Treatment of Waste Copper Electrolytes Using Insoluble and Soluble Anodes

The use of copper anodes with non standard content of impurities for the treatment of waste, sulphur acid solutions that came as a result of the industrial process of electrolytic copper refining was investigated. Those solutions contain the high content of copper, nickel and arsine, and because of that, the copper anodes with high content of Ni, Pb, Sn and Sb were prepared. Examination the effect of high impurities content as well as the influence of the solution temperature on the anodes behaviour during the electrolytic process under the conditions that are the same as the industrial was the aim of this work. Obtained results clearly indicate that tested anodes could be used for the refined during the electrorefining process. Dissolution of copper anodes was not stoppage after the first appearance of the passivation region for A1 and A2 anodes while appearance of passivation for A3 anode, for test duration of 72 h, was not registered. The start time of the first passivation appearance is shorter in the case of the anode with high content of all impurities, anode A1. The first passivation occurrence was detected on higher temperature after about 29 h from the test starts. The change of chemical composition of electrolyte was monitored during electrolysis. Concentration of nickel in the working electrolyte at the end of process is increased and it corresponds to the Ni content in anodes. The copper and arsenic concentrations are decreased during the process. Arsenic passes into the anode slime, while the copper is deposited on the cathode and also passed in the slime. After the process is finished, obtained solution could be used for the nickel recover using the electrochemically or chemically methods

Supplementary data for the article: Nesic, A. R.; Trifunovic, S. S.; Grujic, A. S.; Velickovic, S. J.; Antonovic, D. G. Complexation of Amidated Pectin with Poly(Itaconic Acid) as a Polycarboxylic Polymer Model Compound. Carbohydrate Research 2011, 346 (15), 2463–2468. https://doi.org/10.1016/j.carres.2011.08.021

Supplementary material for: [https://doi.org/10.1016/j.carres.2011.08.021]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1219

Synthesis of nife2o4 nanofibers by joint sol-gel and electrospinning technique

In this study, electrospinning combined with sol-gel technique is applied in order to produce magnetic nickel ferrite (Ni-ferrite) nanofibers. The prepared Ni-ferrite gel was mixed with poly(vinylpyrrolidone) (PVP) solution which was used as a spinning aid to enable spinnability of the mixture. Structural and morphological characteristics of the asspun ferrite gel/PVP composite web structure and calcinated Ni-ferrite nanofibers were analyzed using scanning electron microscopy (SEM). Phase composition analysis was carried out by Fourier-transform infrared (FT-IR) spectroscopy, X-Ray diffraction analysis (XRD) and Fe-57 Mossbauer spectroscopy (MS). The obtained results suggest that the pure nanocrystalline NiFe2O4 dense mat to the almost coral-like structure of fibers with diameters ranging from hundreds of nanometers to few micrometers was obtained. The results of MS analysis revealed the existence of a crystallite size distribution within the material as well as the existence of a superparamagnetic fraction with very small crystallite sizes ( lt 13nm). Magnetic behavior of the obtained material at elevated temperatures was also scrutinized using thermomagnetic measurements (TM) up to 800 degrees C

Complexation of amidated pectin with poly(itaconic acid) as a polycarboxylic polymer model compound

Complexes based on amidated pectin (AP) and poly(itaconic acid) (PIA) were prepared by casting films from solutions of AP and PIA in different ratios with the pectin amount ranging from 10% to 90% by mass. The complexes were investigated by elemental analysis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG). In all investigated ratios of AP/PIA glassy transparent films with a uniform structure were obtained. The results of elemental analysis confirmed the composition of the complexes, and FTIR spectroscopy has shown carboxylic and amide peak shifting, indicating complex formation between AP and PIA. Comparison of thermograms of AP/PIA films with different ratios of AP indicated that the increase of the amount of AP increases the thermal stability of the films by retarding the onset of the main degradation processes.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/2903

THE APPLICATION OF ZEOLITE NANOPOWDER FOR THE CONSTRUCTION OF THE DENSE COMPOSITE POLYMER MEMBRANES FOR CARBON DIOXIDE SEPARATION

The main task of the work is to construct the polymeric membrane that could be used for the waste gases treatment. For this purpose, membrane must have high permeability for the carbon dioxide and low permeability of the other gases commonly present in waste gases (hydrogen, oxygen, nitrogen and methane). The constructed membranes were of a dense type, based on a solubility/diffusivity mechanism. In this paper, feasibility of the application of poly(ethyleneoxid)-copoly(phtalamide) was tested. In order to enchase the permeability of carbon dioxide, four different zeolites were added, and in order to improve mechanical stability two different additives were tested. Three zeolites were with the 3-dimensional pores (ZSM5; Faujasite Linde type A) and one was with the 1-dimensional pores (Linde type L). As an additive, n-tetradecyldimethylamonium bromide -nC14TMABr was tested. The aim of an additive was to provide good wetting of a highly electrically charged zeolite particle by the hydrophobic polymer chains. The other examined additive was dimethylaminopyridine (DMAP) which should improve the solubility of carbon dioxide due to its alkali properties. The best results in carbon dioxide/hydrogen selectivity and permeability were obtained with the membrane constructed with PEBAX 1657 and surface treated zeolite

Hybrid Nd-Fe-B/barium ferrite magnetic materials with epoxy matrix

Lately a great attention has been paid to the research of bonded hybrid composites with improved dynamic mechanical capacities capable of replacing bonded Nd-Fe-B magnetic materials, by using the cheaper (ferrite) materials instead of the Nd-Fe-B powder while retaining the satisfying values of the maximal magnetic energy. The objective of this study is to assess how different contents of Nd-Fe-B and/or barium ferrite particles can affect morphological, dynamic mechanical and magnetic properties of bonded composite materials. The interactions between employed magnetic powders and the interactions between magnetic powders and polymer binder are considered. For the examination of the magnetic behaviour, a vibrating sample magnetometer (VSM) is used. Different shapes and sizes of the obtained hysteresis loops are used for comparison and prediction of the polymer bonded materials properties. The homogeneous distribution of the magnetic particles in the polymer matrix is validated using the scanning electron microscope (SEM). The elastic and damping behaviour examined by the dynamic mechanical analysis (DMA) show improved properties for hybrid composite materials