Yüksek mıknatıslanma doygunluğuna sahip nikel katkılı manganez ferrit tozlarının çözelti yanma sentezi ile üretimi ve karakterizasyonu
Production and characterization of nickel doped manganese ferrite powders with high saturation magnetization by solution combustion synthesis
Yazar: GAMZE DURMAZ
Danışman: YRD. DOÇ. DR. M. ŞEREF SÖNMEZ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı / Üretim Metalurjisi ve Teknolojileri Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2018
Konu: Metalurji Mühendisliği = Metallurgical Engineering

Özet:
Ferritler yaklaşık son 50 yıl boyunca araştırılan ve çeşitli uygulamalarda kendine yer edinen üstün manyetik özelliklere sahip bir oksit sınıfıdır. Günümüzde de ferrit bileşiklerine duyulan ilgi artmaktadır ve teknolojik olarak; daimi mıknatıslar, ferrofluidler, manyetik rezonans görüntüleme, geniş bantlı transformatörler, manyetik sensörler, mikrodalga cihazlar ve enerji depolama, atık sulardan ağır metallerin ve çeşitli organik kirleticilerin giderilmesi, biyosensörler ve kanser tedavisinde ilaç salınımı gibi alanlarda kullanılmaktadırlar.
Elektrokimyasal performanslarından ötürü, genel formülü AB2O4 olan spinel kristal yapılı ikili geçiş metal ferritleri, elektrokimyasal süperkapasitörler için oldukça uygun malzemeler olarak önerilmişlerdir. Elektrokimyasal kapasitörler için potansiyel adaylar olarak MnFe2O4, NiCo2O4, CoFe2O4 vb. spinel bileşikleri düşünülmüştür. Bu bileşikler içerisinde MnFe2O4 özgül kapasitans değerinin > 100 F.g-1 olması , alkali / alkali klorürlerin ve sülfatların sulu solüsyonlarında yüksek enerji yoğunluğu ( >10 kW.kg-1 ) göstermesi nedeniyle ve ayrıca bu elektrokimyasal özelliklerinin yanında, sert redoks ortamında çok kararlı yapısal, elektriksel ve kimyasal özelliklere sahip olması sebebiyle dünya çapında ilgi görmüş bir malzeme olarak karışımıza çıkmaktadır. MnFe2O4 ayrıca, yüksek mıknatıslanma doygunluğu ve düşük blokaj sıcaklığı nedeniyle teknolojik uygulamalar için büyük bir potansiyele sahiptir. MnFe2O4'ün bu manyetik özellikleri esas olarak tetrahedral ve oktahedral alanlar arasındaki katyon dağılımına ve ayrıca kristalit boyutu, morfolojisi ve katkı konsantrasyonuna ve cinsine bağlıdır. Malzemenin elektriksel ve manyetik özelliklerindeki gelişme ise, esas olarak oktahedral ve tetrahedral bölgelerdeki bozulma nedeniyle elde edilmektedir. Ayrıca; katkı ilavesi, katyon yer değiştirmesi veya bileşik hazırlanması ile bu özelliğin geliştirilebileceği bilinmektedir. MnFe2O4 'ün fiziksel ve kimyasal özellikleri, sentez işlemi sırasında doğrudan ve dolaylı olarak da kontrol edilebilen yapısal ve mikro-yapısal özelliklerine de bağlıdır. Bu özellikler yüksek oranda; kompoziyon, morfoloji ve boyut gibi paramatrelere bağlı olarak değişir.
Bu çalışmada, nikel katkılı manganez ferrit bileşilerinin geleneksel yöntemlerden farklı olarak çözelti yanma sentezi yöntemiyle daha kolay, daha saf ve daha ince taneli olarak üretilmesi amaçlanmıştır. Yüksek mıknatıslanma doygunluğu için literatür ile karşılaştırma yapabilmek amacıyla en az 40 emu/g değeri hedeflenmiştir. Böylece, yukarıda bahsedilen alanlarda kullanıma uygun çok saf ve ince taneli nikel manganez ferrit tozlarının üretimi ve karakterizasyonu gerçekleştirilmiştir.

Abstract:
Nanoscience is one of the most important research in modern science. Nanotechnology is beginning to allow scientists, engineers, chemists, and physicians to work at the molecular and cellular levels to produce important advances in the life sciences and healthcare. The use of nanoparticle materials offers major advantages due to their unique size and physicochemical properties. Because of the widespread applications of magnetic nanoparticles in biotechnology, biomedical, material science, engineering, and environmental areas, much attention has been paid to the synthesis of different kinds of magnetic nanoparticles.
Real uses of nanostructured materials in life sciences are uncommon at the present time. However, the excellent properties of these materials provide a very promising future for their use in this field. Nanoclusters are ultrafine particles of nanometer dimensions located between molecules and microscopic structures (micron size). Viewed as materials, they are so small that they exhibit characteristics that are not observed in larger structures (even 100 nm); viewed as molecules, they are so large that they provide access to realms of quantum behavior that are not otherwise accessible. In this size, many recent advances have been made in biology, chemistry, and physics.
Magnetic nanoparticles show remarkable new phenomena such as high field irreversibility, high saturation field, superparamagnetism, extra anisotropy contributions, or shifted loops after field cooling. These phenomena arise from narrow and finite-size effects and surface effects that dominate the magnetic behavior of individual nanoparticles. Frenkel and Dorfman were the first to predict that a particle of ferromagnetic material, below a critical particle size (<15 nm for the common materials), would consist of a single magnetic domain, i.e., a particle that is in a state of uniform magnetization at any field. The magnetization behavior of these particles above a certain temperature, i.e., the blocking temperature, is identical to that of atomic paramagnets (superparamagnetism) except that large susceptibilities and, thus, an extremely large moment are involved.
Ferrites are a class of oxides with superior magnetic properties that have been explored over the last 50 years and take their place in various applications. Nowadays, interest in ferrite compounds is increasing. They are used in permanent magnets, ferrofluids, magnetic resonance imaging, broad - band transformers, magnetic sensors, microwave devices and energy storage, removal of heavy metals and various organic contaminants from wastewater, biosensors and drug release in the treatment of cancer. The most important uses of MnFe2O4 in recent years are; removal of heavy metals and various organic contaminants from wastewater, biosensors and especially drug release in the treatment of cancer.
Binary transition metal ferrites with spinel crystal structure and general molecular formula of AB2O4 have been proposed for electrochemical supercapacitor applications due to their electrochemical performance. MnFe2O4, NiCo2O4, CoFe2O4 etc. spinel compounds have been considered as potential candidates for electrochemical capacitors. In these compounds, MnFe2O4 shows specific capacitances of  >100 F.g-1 and high power densities >10 kW. Kg-1 in aqueous solutions of alkali / alkaline chlorides and sulfates and along with these electrochemical properties, MnFe2O4 has very stable structural, electrical and chemical properties in harsh redox environment. Thanks to these properites, MnFe2O4 stands out as a material of interest in worldwide. MnFe2O4 also has a great potential for technological applications due to its high magnetization saturation and low blocking temperature. These magnetic properties of MnFe2O4 are mainly dependent on the cation distribution between the tetrahedral and octahedral domains and also the crystallite size, morphology, dopant concentration and type. The improvement in the electrical and magnetic properties of the material is mainly due to the deterioration in the octahedral and tetrahedral regions. MnFe2O4 is partially inverse spinel so that the about 80% of Mn2+ ions are located at tetrahedral site while only 20% of them are located at octahedral site. Nanoparticles, nanostructures, and thin films of MnFe2O4 show diverse properties, such as, high anisotropy constant, size-dependent saturation magnetization, super spin glass state, superparamagnetism, and high Curie temperature. These properties of MnFe2O4 result in many attractive applications such as magnetic recording, microwave, magnetic resonance imaging contrast agent, ferrofluid, site specific drug delivery, magnetic tunnel junction-based sensor, photocatalytic, gas sensor and absorbent material for hot-gas. Recently, it was found that MnFe2O4 magnetic nanoparticles were effectively used an excellent adsorbent for the removal of the azo dye Acid Red B from water. Furthermore; it is known that this property can be improved by dopant addition, cation substitution or compound preparation. The physical and chemical properties of MnFe2O4 also depend on the structural and microstructural properties that can be directly and indirectly controlled during the synthesis process. These properties largely depending on parameters such as composition, morphology and size.
The original value of this study, nickel manganese ferrite powders are produced by solution combustion synthesis method as being easier, purer and finer than the conventional methods. Thermochemical examination of the conditions for the synthesis of these powders using different fuels is another unique value that is not exist in the literature (such as reaction enthalpy, flame temperature and generated energy).
 For high magnetization saturation, a value of minimum 40 emu / g will be targeted. Thus, very pure and fine-grained nickel manganese ferrite powders suitable for use in the above-mentioned fields will be produced. MnFe2O4 production will be carried out by solution combustion synthesis method. Self – propagating high temperature synthesis, commonly referred to as combustion synthesis, is used for production of ceramic, intermetallic, composite and functional materials, powders or advanced materials which includes close to the final product.
 Solution combustion synthesis, one of the combustion synthesis types, is an easy, simple and rapid method that enables the production of many materials. This method involves the self - propagating reaction of homogenous solutions of different oxidants (metal nitrates) and fuels (urea, glycine, hydrazide etc.). Depending on the kind of the raw materials and method of implementation way, the solution combustion synthesis takes place in the form of volumetric or layer by layer combustion. Generally, although solution combustion synthesis has a different types, it takes place preparing oxidant and fuel containing mixture solutions, preheat of this solutions and followed by self – propagating reactions, respectively.
Another purpose of this study is to produce powders with superparamagnetic properties. Superparamagnetism appears in small ferromagnetic or ferrimagnetic nanoparticles.If the size of these nanoparticles is small enough, their magnetization can randomly flip direction under the influence of temperature. The time between two flips is known as the Néel relaxation time. If the time used to measure the magnetization of the nanoparticles is much longer than the Néel relaxation time and no external field is present, their average magnetization seems to be zero, and they are said to be in superparamagnetic state.
The concept of superparamagnetism of magnetic materials in the nanoscale was first proposed by Frenkel and Doefman in 1930. They predicted that nanoperticles made of magnetic materials with a particle size small enough would display superparamagnetic properties. Superparamagnetic nanoparticles can be dispersed into an aqueous solution and remain stable by coating them with an appropriate layer, thus forming a ferrofluid. These ferrofluids can be used in different bioapplications, including in vivo and in vitro applications. In vivo applications hold such specialities as drug delivery, hyperthermia procedures, and magnetic resonance imaging as contrast agents.
Normally, any ferromagnetic or ferrimagnetic material undergoes a transition to a paramagnetic state above its Curie temperature. Superparamagnetism is different from this standard transition since it occurs below the Curie temperature of the material. Superparamagnetism occurs in nanoparticles which are single domain, i.e., composed of a single magnetic domain. This is possible when their diameter is below 3-50 nm, depending on the materials. In this condition, it is considered that the magnetization of the nanoparticles is a single giant magnetic moment, the sum of all the individual magnetic moments carried by the atoms of the nanoparticle.
As already mentioned, very fine ferromagnetic particles have very short relaxation times, even at room temperature, and behave superparamagnetically. Their behavior is paramagnetic but their magnetization values are typical of ferromagnetic substances. The individual particles have normal ferromagnetic movements but very short relaxation times, enabling them to rapidly follow directional changes in an applied field. Superparamagnetism is characterized by two significant features. Firstly, there is no hysteresis, which means both retentivity and coercivity are zero. Secondly, magnetization curves measured at different temperatures superimpose when magnetization is plotted as a function of field /temperature. This also demonstrates that superparamagnetism can be destroyed by cooling. The temperature at which this occurs is called the blocking temperature and is dependent linearly on volume and the magnitude of the crystal field anisotropy. For a particle of constant size below the blocking temperature, the magnetization will be stable and shows hysteresis for those particles which have a relaxation time for demagnetization of longer than 100 seconds.
In this study, it is aimed that nickel manganese ferrite powders are produced by solution combustion synthesis method as being easier, purer and finer than the conventional methods. A minimum of 40 emu/g value was targeted for high magnetization saturation and thus, the production and characterization of very pure and fine-grained nickel manganese ferrite powders suitable for use in the above-mentioned areas were carried out.In order to improve the magnetic properties, it was aimed to determine the optimum amount by adding different amounts of nickel to manganese ferrite powder. This powder produced can be used in many different areas as mentioned before. The aim of this study is to eliminate heavy metals and some organic compounds from wastewater.