A study of magneto-crystalline alignment in sintered barium hexaferrite fabricated by powder injection molding

Barium hexaferrite permanent magnets were produced by powder injection molding. Starting barium hexaferrite powder was prepared from a Fe2O3 and BaCO3 powder mixture by calcination followed by milling. The feedstock for powder injection molding was prepared by mixing barium hexaferrite powder with a low viscosity binder. Magnetic alignment was achieved by applying a high intensity magnetic field to the melted feedstock during the injection process. Green samples (with and without magnetic alignment) were subjected to solvent debinding and subsequent thermal debinding followed by sintering. Sintering conditions were optimized in order to achieve a maximum energy product value. Magneto-crystalline aligning in barium hexaferrite was studied on both green and sintered samples using X-ray diffraction, scanning electron microscope (SEM) and magnetic measurements (hysteresis-graphs). All measurements were made both in a parallel and perpendicular direction to the aligning magnetic field. The obtained results confirmed magneto-crystalline alignment

Analysis and modeling of sintering of Sr-hexaferrite produced by PIM technology

The powder injection moulding (PIM) technology is lately becoming more and more significant due to complex design possibilities and good repeatability. This technology requires optimization of all steps starting with material and binder, injection, debinding and sintering parameters. Sintering is one of the key links in this technology. The powder injection moulding process is specific as during feedstock injection powder particles mixed into the binder do not come into mechanical contact. Shrinkage during sintering of PIM samples is high. In this work we have analyzed and modeled the sintering process of isotropic PIM samples of Sr-hexaferrite. The Master Sintering Curve (MSC) principle has been applied to analyze sintering of two types of PIM Sr-hexaferrite samples with completely removed binder and only the extraction step of the debinding procedure (thermal debinding proceeding simultaneously with sintering). Influence of the heating rate on resulting sample microstructures has also been analyzed. Influence of the sintering time and temperature was analyzed using three different phenomenological equations

Spazi e radici tra Citt\ue0 e Campagna nelle Nuove Contraddizioni

Tratta dell'insediamento umano definito dai centri storici della costa tirrenica della provincia di Cosenza. Oltre alla descrizione della realt\ue0 dei centri storici si analizza una ipotesi d'uso del patrimonio edilizio non utilizzato al fine di promuovere nuove forme di stanzialit\ue0 turistica. L'analisi sulla domanda di turismo tiene conto della condizione contemporanea che produce uno straniamento delle radici. Il progetto pertanto fonda le sue intenzioni nella ricostruzione di radici universali che pososno essere ritorvate nelle forme di abitazione proprie del costruito storico

Characterization of the structure and magnetic properties of Fe49Co2V made by the powder metal injection molding route

The semi-hard magnetic alloy Fe49Co2V is widely used in electronics and automation. Many of these parts are complex ones which can be produced with significant advantages by the PIM technology. In this work the feedstock was prepared by mixing the starting powder with a "Solvent System" binder. The injected green samples of toroidal shape were first subjected to solvent debinding. Secondary thermal debinding at optimized temperatures and sintering in the temperature range 1370-1460°C was performed in hydrogen in an Elnik System furnace. Magnetic properties were measured from hysteresis graphs for soft magnetic materials and the main properties such as such as remanent induction Br coercive force Hcb, saturation induction Bs and relative permeability μr were determined. The hysteresis curves obtained were correlated to the microstructures formed during sintering. The results obtained were compared with the data for other technologies of preparing Fe-Co-V from available literature. It is shown that the PIM samples reach magnetic property values comparable to those obtained by conventional methods

Soft magnetic properties of MnZn ferrites prepared by powder injection moulding

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

Recent advances in PIM technology I

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

Recent advances in CIM technology

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

Sintered strontium hexaferrite shaped by injection moulding in unidirectional magnetic and electromagnetic field

Strontium hexaferrite permanent magnets were produced by powder injection molding (PIM). The feedstock for powder injection molding was prepared by mixing strontium hexaferrite powder with a "Solvent system" organic binder. Injection was performed in the cylindrical cavity of the mold both for isotropic and anisotropic green samples. Diametrical alignment was attained using high energy permanent magnets embedded in the mold (unidirectional magnetic field), while axial magnetic alignment was done by DC current passing through a solenoid placed around the cavity (electromagnetic field). Green samples (with and without magnetic alignment) were subjected to solvent debinding and subsequent thermal debinding followed by sintering. Sintering conditions were optimized in order to achieve maximum energy product. Magneto-crystalline aligning in strontium hexaferrite was studied on both green and sintered samples using X-ray diffraction, scanning electron microscopy (SEM) and magnetic measurements (hysteresisgraphs). All measurements were made in the direction parallel to the aligning magnetic field. The obtained results confirmed a high degree of magneto-crystalline alignment

Parallel analysis of axial pressing, casting and PIM as routes for production of alnico8

Samples of Alnico8 were prepared from the same starting powder by pressing, casting and powder injection moulding (PIM), respectively, and characterized by SEM and thermal analysis-DTA/TGA. Optimization of the sintering process was done for reaching the optimum of the energy product (BH)max for each type of samples. During sintering of the PIM specimens, special attention was paid to lowering the contents of residual C and O in the Alnico alloys since these interstitials affect the main magnetic properties. PIM samples were prepared using a feedstock composed of Alnico powder and a Catamold® (BASF) binder. For analysis of the thermal debinding of PIM samples, sintering was done in a dilatometer with coupled mass spectrometer. Shape anisotropy was induced by thermo magnetic treatment of all samples. Subsequently the main magnetic properties were measured and compared mutually and with the best literature results. It was clearly shown from the results obtained that PIM samples can attain the properties of Alnico samples made by classical routes. The microstructure of the sintered PIM samples was analyzed by SEM