Methods of characterization of multiphase Nd-Fe-B melt-spun alloys

Nanocomposite permanent magnetic materials based on Nd-Fe-B alloys with a low Nd content are a new type of permanent magnetic material. The microstructure of these nanocomposite permanent magnets is composed of a mixture of magnetically soft and hard phases providing the so called exchange coupling effect. Beside the optimization process parameters, methods of characterization have a very important role in the design of an optimal magnetic matrix of multiphase melt-spun Nd-Fe-B alloys. Different methods and techniques of characterization were used for observation and study of the microstructure evolution during crystallization. A summary results of measurements using different methods of characterization are presented to enable a better insight into relations between the microstructure and magnetic properties of the investigated melt-spun Nd-Fe-B alloys. .Nanokompozitni permanentni magnetni materijali zasnovani na Nd-Fe B legurama sa niskim sadržajem neodijuma predstavljaju novi tip permanentnih magnetnih materijala. Mikrostruktura ovih nanokompozitnih permanentnih magneta sastoji se iz smeše magnetno meke i magnetno tvrde faze između kojih se javlja "exchange coupling" efekat. Osim optimizacije procesnih parametara, metode karakterizacije imaju veoma veliku ulogu u dizajniranju optimalnog magnetnog matriksa višefaznih melt-spun Nd-Fe-B legura. Različite metode i tehnike karakterizacije korišćene su za posmatranje i proučavanje evolucije miktrostrukture tokom kristalizacije. Sumarni rezultati merenja, dobijeni primenom različitih metoda karakterizacije, prikazani su radi boljeg uvida u povezanost između miktrostrukture i magnetnih svojstava istraživane melt-spun Nd-Fe-B legure.

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

Poređenje metoda za merenje propustljivosti vazduha tekstilnih materijala

The air permeability of textile fabrics is defined as the air passed over a surface under a certain pressure difference in a unit time. Air permeability is often used in evaluating the performance of clothing textiles and technical textiles such as air bags, sail cloth, parachutes sails and industrial textile filters. In practice, which does not have to include scientific research, it is necessary that all tests of textile materials are carried out according to the standards. In the case of air permeability, the most commonly used standard methods are ASTM D737 and ISO 9237 standards. The values of the tested property of a textile material vary very often depending on the device used and method applied. In this research, a comparison of the results of air permeability of some plain knitted fabrics was made, which were obtained using two different devices according to ASTM D737 and ISO 9237 methods. The results obtained indicated the differences in the values of air permeability for all the knitted fabrics. However, the same trend was observed in terms of the observed differences which was confirmed by the high value of the correlation coefficient (r=0.98).Propustljivost vazduha tekstilnih materijala definiše se količinom vazduha koji pri konstantnom pritisku u jedinici vremena prođe kroz jedinicu površine materijala. Ovaj parametar se često koristi za ocenjivanje performansi odevnih tekstilnih materijala i tehničkog tekstila kao što su tkanine za vazdušne jastuke, jedra i padobrane, i industrijski tekstilni filteri. U stručnoj praksi, koja ne uključuje obavezno naučna istraživanja, neophodno je da se sva testiranja tekstilnih materijala vrše prema normama propisanim važećim standardima. Propustljivost vazduha tekstilnih materijala najčešće se ispituje standardnim metodama ASTM D737 i ISO 9237. Vrlo često se dešava da se kvantifikovane vrednosti ispitivanog svojstva tekstilnog materijala razlikuju u zavisnosti od upotrebljenog uređaja, odnosno primenjene standardne metode. Zbog toga je u okviru ovog istraživanja izvršeno poređenje rezultata propustljivosti vazduha grupe DL pletenina, koji su dobijeni primenom dva različita uređaja i dve standardizovane (ASTM D737 i ISO 9237) metode. Poređenjem dve grupe rezultata propustljivosti vazduha DL pletenina uočene su razlike u vrednosti ovog parametra kod svih ispitivanih pletenina. Ipak, zapažen je isti trend u pogledu uočenih razlika u propustljivosti vazduha pletenina, što je potvrđeno visokom vrednošću koeficijenta korelacije (r=0,98)

Gas Separation Properties of the Dense Polymer-Zeolite Powder Composite Membranes

The natural balance in the Earth's atmosphere is significantly influenced by the human emission of the combustion products, mainly carbon dioxide. Therefore, strong efforts are directed in the direction of the reduction of that emission. The solution might be searched in the direction of the construction of the membrane that would be highly transparent to the carbon dioxide, but not transparent to the other gases commonly present in the waste gases (oxygen, nitrogen, hydrogen, methane). One of the feasible designs for this purpose is dense, non-porous membranes, with zeolite particles dispersed in the polymer matrix. Zeolite particles should increase the solubility of the carbon dioxide, and thus enhance its permeability. In this paper, the possibility of application of polyether-b-amide (with 60% of PEG) as a polymer matrix was tested. For the inorganic component, four different zeolite types with three different pore geometries were tested. The influence of the additive which was added in order to provide good contact between the highly polar and charged zeolite inorganic particle, and hydrophobic polymer chains was also tested

Poređenje metoda za merenje propustljivosti vazduha tekstilnih materijala

The air permeability of textile fabrics is defined as the air passed over a surface under a certain pressure difference in a unit time. Air permeability is often used in evaluating the performance of clothing textiles and technical textiles such as air bags, sail cloth, parachutes sails and industrial textile filters. In practice, which does not have to include scientific research, it is necessary that all tests of textile materials are carried out according to the standards. In the case of air permeability, the most commonly used standard methods are ASTM D737 and ISO 9237 standards. The values of the tested property of a textile material vary very often depending on the device used and method applied. In this research, a comparison of the results of air permeability of some plain knitted fabrics was made, which were obtained using two different devices according to ASTM D737 and ISO 9237 methods. The results obtained indicated the differences in the values of air permeability for all the knitted fabrics. However, the same trend was observed in terms of the observed differences which was confirmed by the high value of the correlation coefficient (r=0.98).Propustljivost vazduha tekstilnih materijala definiše se količinom vazduha koji pri konstantnom pritisku u jedinici vremena prođe kroz jedinicu površine materijala. Ovaj parametar se često koristi za ocenjivanje performansi odevnih tekstilnih materijala i tehničkog tekstila kao što su tkanine za vazdušne jastuke, jedra i padobrane, i industrijski tekstilni filteri. U stručnoj praksi, koja ne uključuje obavezno naučna istraživanja, neophodno je da se sva testiranja tekstilnih materijala vrše prema normama propisanim važećim standardima. Propustljivost vazduha tekstilnih materijala najčešće se ispituje standardnim metodama ASTM D737 i ISO 9237. Vrlo često se dešava da se kvantifikovane vrednosti ispitivanog svojstva tekstilnog materijala razlikuju u zavisnosti od upotrebljenog uređaja, odnosno primenjene standardne metode. Zbog toga je u okviru ovog istraživanja izvršeno poređenje rezultata propustljivosti vazduha grupe DL pletenina, koji su dobijeni primenom dva različita uređaja i dve standardizovane (ASTM D737 i ISO 9237) metode. Poređenjem dve grupe rezultata propustljivosti vazduha DL pletenina uočene su razlike u vrednosti ovog parametra kod svih ispitivanih pletenina. Ipak, zapažen je isti trend u pogledu uočenih razlika u propustljivosti vazduha pletenina, što je potvrđeno visokom vrednošću koeficijenta korelacije (r=0,98)

X-Ray Analysis in the Optimization of the Sintering Process of SmCo5 Magnets

The content of the SmCo5 phase, as the carrier of magnetic properties, was controlled by X-ray diffraction analysis. The content of the SmCo5 phase, as a function of sintering time and temperature, under constant heat treatment conditions, was observed through the intensity of its most significant diffraction peak, which corresponds to the (111) plane. By correlating these parameters with a mathematical treatment, a mutual dependence was established. A regression dependence was obtained that showed that the intensity of the diffraction peak of the (111) plane of the SmCo5 phase depends upon the squares of both the sintering time and temperature, for given heat treatment conditions. It is possible to optimize the sintering conditions by calculating values of sintering time and temperature for which this dependence has its maximum

Elektrohemijsko dobijanje prahova legure Co-Ni-Mo-O

The electro deposition of the Co-Ni-Mo-O alloy powders from alkaline ammonium electrolytes and at constant current density was investigated. Metals of iron group, Co and Ni induce deposition of Mo, which alone can not be deposited from water electrolytes. Electrodeposited powders were investigated by SEM analysis where it is possible to determine the particle size, as well as the morphology of powders. The quantitative mass and chemical composition of Co-Ni-Mo-O alloy powders was determined by EDX analysis.Alkalni, amonijačni elektrolit je korišćen za dobijanje prahova Co-Ni-Mo-O legure. Prahovi su taloženi pri konstantnoj gustini struje, kao sporedna reakcija pri reakciji intenzivnog izdvajanja vodonika. Metali grupe gvožđa Co i Ni indukuju taloženje Mo, koji sam ne može da se taloži iz vodenih elektrolita. Dobijeni prahovi su ispitani EDX, X-ray i SEM analizom i na osnovu dobijenih rezultata može se zaključiti da se promenom odnosa koncentracija soli u elektrolitu za taloženje, kao i gustinom struje taloženja može uticati na hemijski sastav i veličinu čestica prahova Co-Ni-Mo-O legure. Rezultati rendgenske analize ukazuju na amorfnu strukturu dobijenih prahova

Structural and phase composition modification of nanocrystalline Nd14Fe79B7 alloy during thermomagnetic measurements

Changes in the microstructure parameters, phase composition and magnetic properties of rapid quenched Nd-rich Nd14Fe79B7 alloy caused by thermomagnetic measurement (TM) were studied using XRD methods of phase analysis, crystallite size and lattice microstrain determination. The observed changes were analyzed between the optimized magnetic state of this alloy and state after TM up to 800oC. Measurement of magnetic properties was carried out on the SQUID magnetometer at ambient temperature. The obtained experimental results show that the investigated alloy in the optimized magnetic state has nearly monophase composition with predominant content of hard magnetic Nd2Fe14B phase (up to 95 mass %) with mean crystallite size below 60 nm. In the state after TM, it was found that the decreased amount of Nd2Fe14B phase (75 mass%), increased amount of soft magnetic phases, predominantly of Fe7Nd5, formation of Nd-rich oxide Nd2O3 phase, as well as grain growth have caused the observed quality loss of hard magnetic properties

Study of microstructure and magnetic properties of optimally annealed R/Q Nd4.5Fe77B18.5 alloy

The rapid-quenched (R/Q) and subsequently optimally annealed Nd-Fe-B alloy with 12 wt% Nd was characterized using the X-Ray diffractometry (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HREM) and superconducting quantum interference device (SQUID) magnetometer. It was found that microstructure of the investigated alloy mainly consist of Fe3B, Nd2Fe14B phases and minor content of α-Fe phase, with mean crystal grain sizes being below 30 nm. The ferromagnetic exchange coupling between the grains of identified hard and soft magnetic phases has direct influence on the magnetic properties as it is illustrated by SQUID hysteresis loop. Correlation of the measured magnetic properties with results of microstructure analysis indicates that the investigated rapid-quenched Nd-Fe-B alloy has the nanocomposite structure in optimal magnetic state