Cold spray additively manufactured pure iron for magnetic applications

Very late stent thrombosis (ST) stent fracture (SF) increases restenosis rate of permanent drug eluting stents (DES). In fact, permanent stents after arterial remodeling (change of artery dimensions during atherosclerosis) process becomes a supportive part inside our body and this idea lead us to develop biodegradable stents which support till arterial remodeling and progressively degrade thereafter. In this research, cold gas dynamic spray technique, simply referred to as cold spray is introduced to spray micro particles on metallic plane and cylindrical substrate. Reference material for permanent stent, stainless steel, 316L is mixed with pure iron in different proportions to induce microgalvanic corrosion effect on as sprayed specimens. Although annealed 316L coatings indicate better ultimate strength, porosity and ductility, their degradation study signifies their poor degradability in Hank’s physiological solution. In contrast to that, immersion and potentiodynamic polarization tests under Hank’s physiological solution indicate that corrosion rate of as sprayed composite increases as amount of iron increases. More iron particles release more iron ions and increases corrosion rate in hanks solution.

Microstructure control of cold-sprayed pure iron coatings formed using mechanically milled powder

New copper–tungsten (W–Cu) composite wires are developed for the winding of non-destructive pulsed magnets. A micrometric Cu powder coated with a nanometric layer of W (1.8 vol%) was used as the starting material. W is chosen for its very high shear modulus, and its introduction at the nanometric scale aims to avoid co-deformation incompatibilities during wire drawing. Composite cylinders were fabricated by cold spraying and then deformed by wire drawing at room temperature, allowing the fabrication of wires.

The cold spray technique is expected to effectively form a metallic coating with fine crystal grains originating from the microstructure of the original powder. We previously reported that a pure iron coating with fine crystal grains can be formed by the cold spray technique by using mechanically-milled pure iron powder. In this study, the tensile strength of the pure iron coating was investigated. The as-sprayed coating showed significantly low Young’s modulus, tensile strength, and ductility owing to the low cohesion strength between particles. For tensile strength improvement, the coating was subjected to spark plasma sintering (SPS) treatment. As a result, the Young’s modulus was considerably improved by the SPS treatments at 740 and 786°C; moreover, the tensile strength of the SPS-treated coating was approximately four times higher than that of the bulk material. In contrast, the ductility was not improved by the SPS treatment. The low ductility was likely attributed to the presence of Fe oxides at the particle–particle interface.

Structural and Optical Properties of Pure Iron and Iron Oxide Nanoparticles Prepared via Pulsed Nd:YAG Laser Ablation in Liquid

Magnetic Materials and Properties for Powder Metallurgy Part Applications

Manufacturing and the process-structure-property correlation of detonation sprayed iron coatings under an unconventional coating deposition mechanism

Mn- and Fe-spinels' formation through sintering of pure and waste materials: Mechanical, electrical and magnetic properties

Synthesis, magnetic and Mössbauer study of ε-Fe xN (2 < x < 3) nanowires

Magnetite (Fe3O4) particles with a diameter around 10 nm have a very low coercivity (Hc) and relative remnant magnetization (Mr/Ms), which is unfavorable for magnetic fluid hyperthermia. In contrast, cobalt ferrite (CoFe2O4) particles of the same size have a very high Hc and Mr/Ms, which is magnetically too hard to obtain suitable specific heating power (SHP) in hyperthermia. For the optimization of the magnetic properties, the Fe2+ ions of magnetite were substituted by Co2+ step by step, which results in a Co doped iron oxide inverse spinel with an adjustable Fe2+ substitution degree in the full range of pure iron oxide up to pure cobalt ferrite. The obtained magnetic nanoparticles were characterized regarding their structural and magnetic properties as well as their cell toxicity. The pure iron oxide particles showed an average size of 8 nm, which increased up to 12 nm for the cobalt ferrite. For ferrofluids containing the prepared particles, only a limited dependence of Hc and Mr/Ms on the Co content in the particles was found, which confirms a stable dispersion of the particles within the ferrofluid. For dry particles, a strong correlation between the Co content and the resulting Hc and Mr/Ms was detected. For small substitution degrees, only a slight increase in Hc was found for the increasing Co content, whereas for a substitution of more than 10% of the Fe atoms by Co, a strong linear increase in Hc and Mr/Ms was obtained. Mössbauer spectroscopy revealed predominantly Fe3+ in all samples, while also verifying an ordered magnetic structure with a low to moderate surface spin canting. Relative spectral areas of Mössbauer subspectra indicated a mainly random distribution of Co2+ ions rather than the more pronounced octahedral site-preference of bulk CoFe2O4. Cell vitality studies confirmed no increased toxicity of the Co-doped iron oxide nanoparticles compared to the pure iron oxide ones. Magnetic heating performance was confirmed to be a function of coercivity as well. The here presented non-toxic magnetic nanoparticle system enables the tuning of the magnetic properties of the particles without a remarkable change in particles size. The found heating performance is suitable for magnetic hyperthermia application.

The first part of this paper is presents a method for producing the composite which shows ferromagnetic, highly-elastic and electrically-conducting properties. This composite consists of ferromagnetic particles of the size 0.15-0.25 mm made of the chemically pure iron. The mentioned particles were dispersed in the elastic porous silicone the matrix with pores of the size 0.15-0.25 mm. Colloidal graphite particles of the size not exceeding 0.5 µm were added to the matrix to increase electrical conductivity. The production method consist in mixing particles of iron, graphite and sodium chloride with non-polymerized silicone and rinsing salt particles by water after the matrix polymerization. In its second part the paper provides a description of the measurement system for longitudinal magnetostriction and the Hall voltage. The magnetic field with the induction of ± 8 T produced by the Bitter type magnet was applied to the composite samples. The supplying voltage was applied to these samples and the Hall voltage was measured at the electrodes glued to them. The longitudinal magnetostriction was measured by means of the capacitor with a variable capacity placed at the upper surface of these samples. The linear magnetostriction exceeding ± 6 % and the Hall voltage reaching ± 5.5 nV were detected by the conducted measurements. Both the longitudinal magnetostriction and the Hall voltage show nonlinear changes and hysteresis lopes during the magnetic field application and the supplying current flow. The coupling of these changes and other regularities observed in the investigated composites and especially their non-linearity and hysteresis, are discussed in the final part of the paper.