Processing and characterization of textured barium ferrite ceramics

Aydoğan, Eda
Technological advances results in the fact that quite a large number of electronic equipment interacts with its environment leading to the malfunction of the devices. This brings about the necessity of using proper electromagnetic (EM) wave absorbers/shields to avoid such interactions. In order to absorb EM waves in a large frequency band from several MHz to GHz, barium hexaferrite (BaHF) ceramics which are produced as textured ceramics as well as in multilayered form can be used. Textured ceramics are processed by tape casting using templated grain growth (TGG) phenomenon. In order to obtain textured ceramics, BaHF powders and platelets are required as raw materials in such a way that during sintering small size powders are directioned by large platelet surfaces. In this study, ferrite powders were synthesized by mixed oxide technique while the platelets were produced by both molten salt synthesis (MSS) and reactive templated grain growth (RTGG) methods. In the case of platelet synthesis by MSS, effects of calcination temperature and time as well as type and composition of the flux on the formation and morphology of platelets were investigated based on the XRD and SEM results. Studies have shown that KCl flux led to the formation of sharper platelet morphology, while NaCl resulted in more round shapes. However, extent of BaHF formation in the case of NaCl was higher when compared to KCl flux due to its higher wettability characteristic, and hence faster interaction with the raw materials. Since the aspect ratio of the synthesized platelets was only ca. 2-4, these platelets were not efficient for further TGG studies. Alternatively, BiFeO3 (BiF) particles having ~30-40 μm average size were synthesized as seed crystals for the synthesis of BaHF platelets by RTGG method. After the washing of these platelets with dilute HNO3, pure BaHF powders and platelets were directed by tape casting which was followed by sintering using TGG phenomenon. Degree of achieved texturing in the processed ceramics was studied using Rietveld analysis, pole figure measurement and electron backscattered diffraction (EBSD).


Modeling and control of high temperature oven for low temperature co-fired ceramic (LTCC) device manufacturing
Yücel, Ayşe Tuğçe; Kıncal, Serkan; Department of Chemical Engineering (2012)
In the electronics the quality, reliability, operational speed, device density and cost of circuits are fundamentally determined by carriers. If it is necessary to use better material than plastic carrier, it has to be made of ceramics or glass-ceramics. This study dealt with the ceramic based carrier production system. The types of the raw ceramics fired at low temperature (below 1000°C) are called Low Temperature Co-Fired Ceramics (LTCC). In this study, a comprehensive thermal model is described for the h...
Identification of materials with magnetic characteristics by neural networks
Nazlibilek, Sedat; EGE, Yavuz; Kalender, Osman; Sensoy, Mehmet Gokhan; Karacor, Deniz; Sazh, Murat Husnu (2012-05-01)
In industry, there is a need for remote sensing and autonomous method for the identification of the ferromagnetic materials used. The system is desired to have the characteristics of improved accuracy and low power consumption. It must also autonomous and fast enough for the decision. In this work, the details of inaccurate and low power remote sensing mechanism and autonomous identification system are given. The remote sensing mechanism utilizes KMZ51 anisotropic magneto-resistive sensor with high sensitiv...
Silver Nanowire/Conducting Polymer Nanocomposite Electrochromic Supercapacitor Electrodes
YÜKSEL, Recep; COŞKUN, Sahin; Günbaş, Emrullah Görkem; Çırpan, Ali; Toppare, Levent Kamil; Ünalan, Hüsnü Emrah (The Electrochemical Society, 2017-01-01)
Color-changing energy storage devices that can easily communicate with the user carry the potential to be integrated into smart electronics. In this work, nanocomposite electrochromic supercapacitor electrodes were fabricated with silver nanowire (Ag NW) network electrodes and a green to transmissive electrochromic polymer, PDOPEQ. High transparency and conductivity of Ag NW network current collectors allowed the fabrication of electrochromic supercapacitors and investigation of the spectroelectrochemical a...
Implementation of an Enhanced Target Localization and Identification Algorithm on a Magnetic WSN
Baghaee, Sajjad; GÜRBÜZ, SEVGİ ZÜBEYDE; Uysal, Elif (2015-10-01)
Wireless sensor networks (WSNs) are ubiquitous in a wide range of applications requiring the monitoring of physical and environmental variables, such as target localization and identification. One of these applications is the sensing of ferromagnetic objects. In typical applications, the area to be monitored is typically large compared to the sensing radius of each magnetic sensor. On the other hand, the RF communication radii of WSN nodes are invariably larger than the sensing radii. This makes it economic...
Design and simulation of a vapor compression refrigeration cycle for a micro refrigerator
Yıldız, Seyfettin; Okutucu Özyurt, Hanife Tuba; Department of Mechanical Engineering (2010)
Cooling of electronic equipments has become an important issue as the advances in technology enabled the fabrication of very small devices. The main challenge in cooling is the space limitation. The use of miniature refrigerators seems to be a solution alternative for the cooling problem. The objective of this study is to design and simulate a vapor compression refrigeration cycle for a micro-scale refrigerator. A MATLAB code is developed for the simulations. The four components of the refrigerator, namely,...
Citation Formats
E. Aydoğan, “Processing and characterization of textured barium ferrite ceramics,” M.S. - Master of Science, Middle East Technical University, 2012.