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.

TECHNO-ECONOMIC OPTIMIZATION OF ENERGY SUPPLY OF A LIVESTOCK FARM

Livestock farming is a significant part of agriculture market in Serbia. A descending trend of livestock species was recorded recently, despite its potential for export of meet. Application of new technologies could improve competitiveness of livestock farming. In this paper, energy efficient energy supply technologies and potentials for their application in livestock farms is analyzed. A methodology for pinpointing profitable energy supply options which also provides significant energy and CO2 savings is proposed. A case study of a pig farm was used to perform an energy balance and allocation of energy supply costs. Potentials for application of energy supply technologies based on local resources were estimated in the study. Effects of integration of proposed technologies were also estimated. The proposed methodology was used to analyze feasibility of proposed energy supply options. Investment in a biogas cogeneration plant showed best profitability. Integrated option which envisages application of heat pump for heat supply and photovoltaic solar collectors for production of electricity showed best energetic and environmental performance, while maintaining financial feasibility

TECHNO-ECONOMIC OPTIMIZATION OF ENERGY SUPPLY OF A LIVESTOCK FARM

Livestock farming is a significant part of agriculture market in Serbia. A descending trend of livestock species was recorded recently, despite its potential for export of meet. Application of new technologies could improve competitiveness of livestock farming. In this paper, energy efficient energy supply technologies and potentials for their application in livestock farms is analyzed. A methodology for pinpointing profitable energy supply options which also provides significant energy and CO2 savings is proposed. A case study of a pig farm was used to perform an energy balance and allocation of energy supply costs. Potentials for application of energy supply technologies based on local resources were estimated in the study. Effects of integration of proposed technologies were also estimated. The proposed methodology was used to analyze feasibility of proposed energy supply options. Investment in a biogas cogeneration plant showed best profitability. Integrated option which envisages application of heat pump for heat supply and photovoltaic solar collectors for production of electricity showed best energetic and environmental performance, while maintaining financial feasibility

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

NdFeB permanent magnets with various Nd content

Three kinds of commercial Nd-Fe-B based materials were compared using 57Fe Mössbauer spectroscopy and X-ray analysis: near the Nd 2Fe14B stoichiometry and with both lowered and raised Nd content. Magnetically hard Nd2Fe14B is present in all three materials. In the Nd-low material it is accompanied with the magnetically soft Fe3B phase, building the nanocomposite structure. In the Nd-rich sample the overstoichiometric Nd atoms seem to build separate phase of Fe-Nd solid solution. None of the materials contain significant content of phases degrading magnetic characteristics, with except of minor Nd1.1Fe 4B4 one

The influence of chemical composition on microstructure, hardness and electrical conductivity of Ag-Bi-In alloys at 100 °C

Considering possible applications and scarceness of literature data, Ag-Bi-In system was investigated in terms of microstructure, mechanical and electrical properties of ternary alloys from an isothermal section at 100oC. Based on the experimentally obtained results hardness and electrical conductivity of all ternary alloys from the ternary Ag-Bi-In system at 100oC were predicted. In addition, the selected isothermal section was further thermodynamically assessed and experimentally studied using scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), X-ray powder diffraction (XRD) analysis and light optical microscopy (LOM). Phase transition temperatures of alloys with overall compositions along vertical sections x(Ag)=0.5 as well as liquidus temperatures were experimentally determined by DTA. The experimentally obtained results were compared with literature data and with the results of thermodynamic calculation of phase equilibria based on CALPHAD method and corrected data for Ag-In binary system. Calculated liquidus projection, invariant equilibria and phase diagram of the Ag-Bi-In ternary system are presented as well

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

Effect of chemical composition on microstructure, hardness and electrical conductivity profiles of the Bi-Cu-Ga alloys at 100 °C

Theoretical calculation and experimental investigation of the isothermal section of a ternary Bi-Cu-Ga system at 100 oC are presented in this paper. Thermodynamic binary-based calculation of the isothermal section was performed using Pandat software. Experimental investigation included microstructural analysis carried out using light optical microscopy (LOM) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), phase composition analysis using X-ray diffraction (XRD), Brinell and Vickers hardness testing and electrical conductivity measurements. In total, thirty alloy samples with compositions along three vertical sections Bi-CuGa, Cu-BiGa and Ga-BiCu were studied. The obtained experimental results support the calculated phase regions of the isothermal section at 100 oC. Hardness of individual phases as well as hardness and electrical conductivity of the studied alloys were measured. Based on the experimentally obtained results iso-lines of Brinell hardness and electrical conductivity along the whole compositional range were calculated by using appropriate mathematical models

Thermomagnetic behaviour and microstructure of a rapidly quenched Nd4.5Fe77B18.5 alloy

Changes in the phase composition and crystallite size, as well as changes in the magnetic behaviour of Nd4.5Fe77B18.5 alloy, caused by thermomagnetic measurements, was observed in regard of the optimal magnetic state of this alloy. In the optimized magnetic state, the formed nanocomposite consisted of Fe3B/Nd2Fe14B and partly of alpha-Fe with a mean crystallite size LT 30 nm, as determined by X-ray diffraction and transmission electron microscopy. An increased amount of alpha-Fe, the presence of Nd2O3 and different Fe-B phases, as well as an increase in the mean crystallite size were observed after thermomagnetic measurements had caused a quality loss of the hard magnetic properties

Phase equilibria investigation and characterization of the Au-In-Sb system

The Au-In-Sb system is of great interest recently, because its alloys belong to the group of potential lead-free solder materials to be used in electronics, while as a part of Au-ln-Sb-Te system, it presents a suitable phase change material in optical recording media. The results of phase equilibria investigation and characterization of the alloys in the AuIn-Sb section of the Au-In-Sb system are presented in this paper. The investigations were performed using different experimental methods - thermal analysis, optical microscopy and SEM-EDX, hardness and electrical conductivity measurements, and also, using ThermoCalc software based on adequate thermodynamic calculation