Nowadays magnetic refrigeration which is based on the Magnetocaloric Effect (MCE) is one of the more relevant topics in the scientific research owing to its very important technological applications, which derive from the attempts made to replace the gas refrigerating technology involving, among other transcendental aspects, a low impact in the environment and an expected higher energetic efficiency. Furthermore, new and improved magnetocaloric materials are one of the cornerstones in the development of room temperature magnetic refrigeration. This master’s work has mainly been concerned in a development of a deep and systematic study of magnetic and magnetocaloric properties of ribbon samples of Heusler alloy family of materials with compositions susceptible of exhibiting MCE, For this purpose, we have focused on ribbons of chemical composition Co50Mn30InxSn (20-x) (x= 0, 5, 10, 15, and 20).
Co50Mn30InxSn (20-x) Heusler alloys were prepared by arc melting admixtures of the pure elements in the desired quantities under argon atmosphere. The ribbons have been prepared by melt spinning technique. X-ray characterization proved the face centered cubic austenite Heusler alloy phase (211) crystal structural with lattice constant a = 0.5947 nm of as cast and annealed ribbons. Differential Scanning Calorimetry was used to find the temperatures of the recrystallization phase transitions. Magnetization was measured for as-cast and annealed samples. Both Curie temperatures and coercivity were found to be lower in the as-cast samples than in the glass tube annealed ones. Monotonic decreasing of the Curie temperature was observed in the series with the growth of the content.
MCE has been evaluated for one of the samples (x = 15) and a maximum value of entropy change is 2.37 JKg-1K-1 have been found, which is the same order of magnitude that reported of Gd alloys.
Table of Contents
Chapter One: Magnetocaloric effect and Heusler alloy
1.1 Introduction
1.2 Thermodynamics of magnetocaloric effect
1.3 Measurements of MCE
1.4 Magnetic Refrigeration and Materilas
1.5 Magnetocaloric materials
1.6 Heusler alloy
1.7 Aim of the work
Chapter Two: Sample Preparation and Experimental Techniques
2.1 Preparation of samples
2.1.1 Arc melter
2.1.2 Melt Spinner
2.1.3 Sample Preparation
i) Master alloy
ii) Ribbon Preparation
2.2 Instrumentations
2.2.1 Preparation of system for annealing sample
2.2.2 Differential Sanning Calorimetry
2.2.3 Powder X-ray diffractometer
2.2.4 Physical Property Measurement System(PPMS)
2.2.5 Vibrating Sample Magnetometer(VSM)
Chapter Three: Results and Discussion
3.1 DSC Results
3.2 XRD Results
3.3 Magnetic Measurements
3.3.1 Hysteresis Behavior
3.3.2 Isothermal magnetization measurement
3.3.3 Thermal dependence of the magnetization measurement
3.4 MCE measurements Results
Chapter Four: General Conclusion and Future work
Research Objectives and Thematic Areas
This thesis aims to conduct a deep and systematic investigation of the magnetic and magnetocaloric properties of Co50Mn30InxSn(20-x) Heusler alloy ribbons. The primary objective is to evaluate these materials for potential applications in magnetic refrigeration technology by analyzing their structural and magnetic behaviors under various experimental conditions.
- Thermodynamics and measurement methods of the Magnetocaloric Effect (MCE).
- Synthesis and preparation techniques, including Arc Melting and Melt Spinning.
- Structural characterization using Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD).
- Magnetic property analysis via Physical Property Measurement System (PPMS) and Vibrating Sample Magnetometer (VSM).
- Evaluation of phase transitions and their impact on magnetic cooling efficiency.
Excerpt from the Thesis
1.1 Introduction
Magnetic refrigeration which is based on the Magnetocaloric effect (MCE) is one of the more relevant topics in the scientific research owing to its very important technological applications, which derive from the attempts made to replace the gas refrigerating technology involving, among other transcendental aspects, a low impact in the environment and an expected higher energetic efficiency. The magnetocaloric effect or adiabatic temperature change is defined as the intrinsic property of magnetic materials which is expressed by its variance under the action of an external magnetic field which means that MCE is the heating or cooling (i.e., the temperature change) of a magnetic material due to the application of a magnetic field [1,2].
In 1881 Warburg was originally first observed the magnetocaloric effect or adiabatic temperature change by the application of a magnetic field in iron [1]. The origin of the MCE was explained independently by Debye and Gaiauque in 1926 and 1927 respectively. They also suggested the first practical use of the MCE: the adiabatic demagnetisation, which means that it is able to reach temperatures, lowers than that of liquid helium, which had been the lowest achievable experimentally temperature. It is the response of a magnetic material to a changing field that is evident as a change in its temperature in the vicinity of the Curie temperature [2-5].
Summary of Chapters
Chapter One: Magnetocaloric effect and Heusler alloy: Provides the theoretical background of the magnetocaloric effect, thermodynamics of MCE, and an overview of Heusler alloys.
Chapter Two: Sample Preparation and Experimental Techniques: Describes the methodology for synthesizing the alloy samples and the instrumentation used for characterization.
Chapter Three: Results and Discussion: Presents the findings from DSC, XRD, and magnetic measurements, analyzing phase transformations and MCE performance.
Chapter Four: General Conclusion and Future work: Summarizes the key findings of the structural and magnetic analysis and proposes directions for future research.
Keywords
Magnetocaloric effect, MCE, Heusler alloy, magnetic refrigeration, Co50Mn30InxSn(20-x), arc melting, melt spinning, thermodynamics, differential scanning calorimetry, DSC, X-ray diffraction, XRD, vibrating sample magnetometer, VSM, phase transition.
Frequently Asked Questions
What is the core focus of this research?
This work investigates the magnetic and magnetocaloric properties of Co50Mn30InxSn(20-x) alloy ribbons to determine their suitability as materials for magnetic refrigeration.
What are the central thematic fields?
The research encompasses materials science, thermodynamics of magnetic systems, experimental characterization techniques, and the development of energy-efficient refrigeration alternatives.
What is the primary goal of the thesis?
The main objective is to develop a deep and systematic study of the magnetic and magnetocaloric properties of Heusler alloy ribbons to evaluate their potential for competitive commercial refrigeration.
Which scientific methods are employed?
The study uses arc melting and melt spinning for sample preparation, followed by DSC for thermal analysis, XRD for structural investigation, and VSM/PPMS for magnetic characterization.
What topics are covered in the main body?
The main body covers the theoretical background of the magnetocaloric effect, detailed descriptions of sample synthesis, comprehensive characterization results, and the discussion of experimental data.
Which keywords characterize this work?
Key terms include Magnetocaloric effect, Heusler alloy, magnetic refrigeration, DSC, XRD, VSM, and phase transition analysis.
How does Indium content affect the magnetic properties of the samples?
The thesis finds that the Indium content influences the Curie temperature and the magnetic saturation of the samples, with certain concentrations proving more favorable for displaying high magnetocaloric effects.
What did the XRD analysis reveal about the crystalline structure?
XRD analysis confirmed the presence of the austenitic phase with L21 crystal structure in the samples, providing insight into the structural stability after heat treatment.
What impact does annealing have on the material properties?
Annealing was found to affect the grain size and phase transformation complexity, leading to different magnetic behaviors compared to the as-cast samples.
- Arbeit zitieren
- Mst. Nazmunnahar (Autor:in), 2010, Structural and Magnetic Characterization of Co50Mn30InxSn(20-x) (x= 0, 5, 10, 15, and 20) Samples for Magnetocaloric Effect, München, GRIN Verlag, https://www.hausarbeiten.de/document/181811
