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In this work we have analyzed the effects of Ti doping on structural and electrical properties of α-Fe2O3. When the amount of added Ti (5 wt.%TiO2) was within the solubility degree and XRD, SEM and EDS analysis revealed a homogenous hematite structure, with lattice parameters a= 5.03719(3) Å, c=13.7484(1) Å slightly increased due to incorporation of Ti into the rhombohedral hematite lattice. Higher amounts of Ti (10 wt.%TiO2) resulted in the formation of pseudobrookite, besides hematite, confirmed by SEM and EDS analysis. Studies of electric properties in the temperature range 25-225oC at different frequencies (100 - 1Mz) showed that Ti doping improved electrical conductivity. Impedance analysis was performed using an equivalent circuit, showing one relaxation process and suggesting dominant grain boundary contribution. [Projekat Ministarstva nauke Republike Srbije, br. III45014 i br. III43008]

In this study, properties of soft-magnetic manganese zinc ferrite manufactured by powder injection moulding - PIM technology were presented. A powder consisting of Mn1- xZnxFe2O4 with small addition of hematite □-Fe2O3 was mixed with an organic binder (wax and thermoplastic) to form ferrite feedstock. The ferrite feedstock was injected in a mould with a cavity shaped like a small cylinder with a hole on the main axis. Injection moulded samples were then solvent, thermally debinded and sintered in air atmosphere. Structure of sintered sample was characterized using X-ray diffractometry, scanning electron microscopy and thermomagnetic measurements. Magnetic properties were measured by hysteresis graph at different frequencies up to 1 kHz. Sintered sample contains a mixture of two phases Mn0.6Zn0.4Fe2O4 (68 wt. %) and α-Fe2O3 (32 wt. %). The Curie temperature is TC ≈ 220°C for the green sample but after the heating up to 470°C, TC increase up to about 300°C. The high increase of normalized magnetic permeability of about 800 % was observed due to melting and burning of binder. The hysteresis loop of sintered MnZn ferrite toroidal cores has an R-shape with saturation of 0.44 T and remanence ratio of 0.49. The low value of coercivity (only 47 A/m) was related to the presence of α-Fe2O3 crystalline phase and attained already optimum density (ρ ≈ 4.8 g/cm³) i.e. observed low level of porosity. Attained relative magnetic permeability μr ≈ 2000 as well as power losses Ps ≈ 21 W/kg for sintered sample (at 1 kHz; 0.39 T) is in agreement with the MnZn ferrite commercial samples. [Projekat Ministarstva nauke Republike Srbije, br. OI 172057]

In this article the PIM (Powder Injection Moulding) technology is described in brief. After that the benefits and advantages were analyzed and summarized. Ceramic injection moulding (CIM) process was analyzed in more detail: CIM- alumina, CIM-zirconia and CIM ferrites as the most common technical ceramics in CIM ceramic parts production, medical applications and accessories in chemical laboratories, and cores in electronic inductive components. After that our results for CIM barium hexaferrite and piezo ceramics (barium titanate) are given. The main powder characteristics, the shrinkage and density and the main electrical characteristics of the sintered samples were compared for the isostatically pressed PM (powder metallurgy) and CIM formed samples. SEM fractographs of CIM and PM samples are given for CIM green parts, debinded (white) parts and sintered parts, and PM green parts and sintered parts. The results obtained were compared to literature data before they were applied in ceramic components production.

Traditionally, the common alloy elements for sintered steels have been Cu and Ni. With increasing requirements towards mechanical properties, and also as a consequence of soaring prices especially for these two metals, other alloy elements have also become more and more attractive for sintered steels, which make the steels however more tricky to process through PM. Here, the chances and risks of using in particular Cr and Mn alloy steels are discussed, considering the different alloying techniques viable in powder metallurgy, and it is shown that there are specific requirements in particular for sintering process. The critical importance of chemical reactions between the metal and the atmosphere is described, and it is shown that not only O2 and H2O but also H2 and even N2 can critically affect sintering and microstructural homogenization.

In this article the state of art of the PIM (Powder Injection Moulding) technology is given in brief. The main process flow diagram consisting of four steps: feedstock preparation, injection moulding (green samples forming), the debinding (binder removing) procedure and the sintering process was described. After that the materials for binders and additives for the surface active agents were mentioned in brief. The metal injection moulding (MIM) process was analysed in more detail: MIM- stainless steels, MIM-copper and MIM-aluminium as the most metals common in MIM metal parts production. After that our results of MIM stainless steel 316 L and MIM copper are given. The main powder characteristics, the shrinkage and density of the sintered samples were compared for isostatically pressed PM (powder metallurgy) samples and MIM formed samples. The SEM fractographs of MIM and PM samples are given for MIM green parts, debinded (brown) parts and sintered parts, and PM green parts and sintered parts. The results obtained were compared with literature data before they were applied in metal parts production.