**2. Recycled material resource: Mn-Zn ferrite**

Ferrites are ceramic, homogeneous materials composed of various oxides with iron oxide as their main constituent. Ferrites have several distinct crystal structures. However, for this chapter, only the Mn-Zn ferrites of cubic crystal structure are concerned. Mn-Zn ferrites are used for frequencies less than 2 MHz and at room temperature have a resistivity lower at 105 Ωm [9]. Their first practical application was as inductors used in LC filters for frequency division multiplex equipment. The combination of high resistivity and good magnetic properties made these ferrites an excellent material for these filters operating over the 50–450 kHz frequency range. For five decades ferrite components have been employed in a widening range of applications [10]. Currently these are useful as magnetic devices into applications such as switching mode power supplies (SMPS) and lighting electronic ballasts, matching and storage devices, interference suppression, etc.

health impacts have restricted the wide-scale production [3, 4]. In response to those concerns, coherent procedures that enable device manufacturers to reduce or eliminate toxic substances in

It is well known that for the materials selection for conventional electronic devices, the primary purpose is link material and function. The latter has been achieved by focusing on selected material attributes, including mechanical, thermal, electrical, optical, and chemical properties, and processing characteristics [5]. Also, traditionally selection has been focused solely on cost; nevertheless, availability, environmental consequences of use, and recycling must also become important factors. Recycling is the transformation of waste into usable products or materials; it is sometimes referred as resources recovery which might be often more environmentally gentle than using raw materials owing to reduced energy use and

The assessment of recycling potential must be based on established principles, including knowledge of the relative ease of "liberation" of the materials of interest and specific characteristics during physical separation technology and shredding in accordance with the international materials life-cycle initiative established by the United Nations Environmental Program (UNEP) and the Society for Environmental Toxicology and Chemistry (SETAC) [7]. Conversely, design of products profoundly will affect the potential recyclability of the

The chapter is focused on recovery of one useful material based on iron oxide well known as Mn-Zn ferrite extracted from unusable electronic systems. Using a scientific tool known as life-cycle assessment (LCA), which takes into account all stages of the life cycle of products or materials, including processing technology, manufacturing processes, use phase, and end-of-life routes, will deliver powerful basis to quantifying the recycling performance. Thus, researching Mn-Zn ferrites in foil shape will provide theoretical basis for open-loop recycling,

This chapter is organized as follows. After introducing the recycling concept and their environmental advantages, it presents the Mn-Zn foil ferrites as recycled material resource explaining the source of their uncommon physical properties. Then the following sections are focused on analysis of both structure and conduction properties to functional green devices

Ferrites are ceramic, homogeneous materials composed of various oxides with iron oxide as their main constituent. Ferrites have several distinct crystal structures. However, for this chapter, only the Mn-Zn ferrites of cubic crystal structure are concerned. Mn-Zn ferrites are used

Their first practical application was as inductors used in LC filters for frequency division multiplex equipment. The combination of high resistivity and good magnetic properties made these

Ωm [9].

for frequencies less than 2 MHz and at room temperature have a resistivity lower at 105

their designs will be a major advance toward green development.

elimination of hazardous gases and other pollutants [6].

converting waste materials into suitable materials in its second life.

**2. Recycled material resource: Mn-Zn ferrite**

resources they contain [8].

190 Iron Ores and Iron Oxide Materials

into engineering applications.

It is well known that the magnetic structure of a Mn-Zn ferrite is noncollinear in a certain range of temperatures and magnetic fields, which results from competitions between antiferromagnetic interactions of their sublattices, aligning the sublattice magnetizations antiparallel to each other, and under an external field will try to align them parallel to each other [11]. Such magnetic interactions between d ions had allow to predict magnetic properties and thus to calculate composition with structure parameters; however, dominant interaction is exchange coupling between Mn and Fe ions caused by the magneto-crystalline anisotropy. Furthermore, it has been shown that the states of Mn and Fe ions support both ferromagnetic and antiferromagnetic long-range orders [12]. At lower field conditions, bulk ferrites always are accompanied by characteristic anomalies in their physical properties, like domain structure [13]. The last indicates that the resistivity in their grain boundaries will be short-circuited due to the domain wall excitation by the applied alternating magnetic field when the frequency changes from 10 kHz to 1 MHz [14].

Mn-Zn ferrites have been manufactured by a complex composition of iron oxide (*Fe*<sup>2</sup> *<sup>O</sup>*<sup>3</sup> ) mixed with manganese oxide (MnO) and zinc oxide (ZnO) by using ceramic process technologies. Ceramic process can be divided into four functions: preparation of the powder, forming powder into cores, sintering cycle, and finishing stage [9, 10]. Thus, taking into account environmental impacts, the use of energy resources, etc., efficiency in the processing technology of bulk ferrites must be studied into LCA methodology, including product manufacturing, use phase, and end of life. **Figure 1** illustrates the schematic of the life-cycle assessment methodology for bulk ferrites.

LCA methodology with the stages coverage in **Figure 1** is understood in accordance with the following. During the preparation of the powder, raw material (*Fe*<sup>2</sup> *<sup>O</sup>*<sup>3</sup> ) and MnO and ZnO oxides as constitutes are weighed and thoroughly mixed into a homogeneous mixture to form slurry and then mixed in a ball mill [9, 15]. After calcining process in air atmosphere at the powder temperature of approximately 1000° C, partial decomposition of the carbonates and oxide evaporation of impurities occurs.

Besides, forming powder into core geometries is done by dry pressing process, and to achieve final magnetic and mechanical characteristics in bulk ferrites, sintering cycle must be completed. This phase consists in gradual ramping up from room temperature to approximately 800° C into air atmosphere. After, the temperature is further increased to the final temperature cycle from 1000 to 1500° C, after a cool-down cycle is needed at reduced oxygen pressure. Finally, most ferrites will require some shape of finishing in accordance with their magnetic performance. Subsequently, the Mn-Zn bulk ferrites are in general employed as SMPS into product manufacture (see **Figure 1**). However, severe problems as the combination of core losses (hysteresis, eddy currents, and residual), winding losses, and failures in power semiconductor

structure must be evaluated using a recycling model to identify critical parameters in view of recycling performance and resource efficiency; therefore, a methodology such as Life-Cycle Green Strategy (LCGS) is proposed here. **Figure 2** illustrates the recycling model based on LCGS for recovery of Mn-Zn foil ferrites from bulk ferrites. The recycling model represents the liberation of bulk ferrites during different phases from dismantling, physical separation, and shredding phase as a function of the device-manufacture characteristics, specifically the parameters that will characterize the foil ferrites as physical dimensions to operability into an

Mn-Zn Ferrite as Recycled Material Resource Based on Iron Oxide Suitable to Functional Green…

http://dx.doi.org/10.5772/intechopen.72418

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Ferrites with E core geometry of different dimensions have been recovered from three systems: LC filter, lighting electronic ballast, and SMPS. The foil ferrites with area of 5 x 5 *mm*<sup>2</sup> and thickness of 1 mm are processed by using shredding phase. Shredding phase consists in cut into the small bulk ferrite pieces to get ease fracture pathways along each piece. The fracture strength will be depending on carefully applied mechanical stress, and when the critical fracture length occurs, uniform foil ferrites of different dimensions and thickness are attained. The following sections in this chapter will demonstrate technological potential of foil ferrites to design suitable functional green devices. Therefore, due to the arduous task in composition

**Figure 2.** Schematic of recycling model based on LCGS as applied to recovery of foil ferrite samples.

electronic signal processor (see **Figure 2**) [18].

**Figure 1.** Schematic of the LCA methodology as applied to Mn-Zn bulk ferrite production including manufacturing stages and final disposal.

devices under extreme switching conditions increase losses by temperature rise resulting in thermal runaway which reduce end of life of the consumer electronics [16].

The LCA studies confirm that the processing technology of Mn-Zn bulk ferrites in their first life, including powder preparation, SMPS manufacturing, and final disposition of constituent materials, results in negative environmental impact such as emission of toxic gases during powder preparation, higher use of energy resources into sintering cycle, and electronic waste by the poorly processing technology and inadequate design of SMPS which has taken at the final placement of such these ferrites often in landfills as shown in **Figure 1**.

From earlier studies it has been identified that power losses in Mn-Zn ferrites under lowfrequency excitation are close to zero, because chemical composition and oxidation degree depend on temperature like semiconductor materials; then a small grained ferrite (<5 μm) with a single magnetic domain structure would be capable to drive at low frequencies (< 10 kHz) when bulk ferrites are converting in foil ferrites [15, 17]. Hence, such grain-reduced crystalline structure must be evaluated using a recycling model to identify critical parameters in view of recycling performance and resource efficiency; therefore, a methodology such as Life-Cycle Green Strategy (LCGS) is proposed here. **Figure 2** illustrates the recycling model based on LCGS for recovery of Mn-Zn foil ferrites from bulk ferrites. The recycling model represents the liberation of bulk ferrites during different phases from dismantling, physical separation, and shredding phase as a function of the device-manufacture characteristics, specifically the parameters that will characterize the foil ferrites as physical dimensions to operability into an electronic signal processor (see **Figure 2**) [18].

Ferrites with E core geometry of different dimensions have been recovered from three systems: LC filter, lighting electronic ballast, and SMPS. The foil ferrites with area of 5 x 5 *mm*<sup>2</sup> and thickness of 1 mm are processed by using shredding phase. Shredding phase consists in cut into the small bulk ferrite pieces to get ease fracture pathways along each piece. The fracture strength will be depending on carefully applied mechanical stress, and when the critical fracture length occurs, uniform foil ferrites of different dimensions and thickness are attained.

The following sections in this chapter will demonstrate technological potential of foil ferrites to design suitable functional green devices. Therefore, due to the arduous task in composition

**Figure 2.** Schematic of recycling model based on LCGS as applied to recovery of foil ferrite samples.

devices under extreme switching conditions increase losses by temperature rise resulting in

**Figure 1.** Schematic of the LCA methodology as applied to Mn-Zn bulk ferrite production including manufacturing

The LCA studies confirm that the processing technology of Mn-Zn bulk ferrites in their first life, including powder preparation, SMPS manufacturing, and final disposition of constituent materials, results in negative environmental impact such as emission of toxic gases during powder preparation, higher use of energy resources into sintering cycle, and electronic waste by the poorly processing technology and inadequate design of SMPS which has taken at the

From earlier studies it has been identified that power losses in Mn-Zn ferrites under lowfrequency excitation are close to zero, because chemical composition and oxidation degree depend on temperature like semiconductor materials; then a small grained ferrite (<5 μm) with a single magnetic domain structure would be capable to drive at low frequencies (< 10 kHz) when bulk ferrites are converting in foil ferrites [15, 17]. Hence, such grain-reduced crystalline

thermal runaway which reduce end of life of the consumer electronics [16].

stages and final disposal.

192 Iron Ores and Iron Oxide Materials

final placement of such these ferrites often in landfills as shown in **Figure 1**.

finding of the Mn-Zn ferrites, predicting theoretically their uncommon properties is a possibility in foil ferrite analysis; then studying structure and conduction properties makes it possible to estimate their physical behavior.
