Ferritic Copper Research Articles

Multicatalysis Combining 3D-Printed Devices and Magnetic Nanoparticles in One-Pot Reactions: Steps Forward in Compartmentation and Recyclability of Catalysts

A tricatalytic compartmentalized system that immobilizes metallic species to perform one-pot sequential functionalization is described: a three-dimensional (3D)-printed palladium monolith, ferritic copper(I) magnetic nanoparticles, and a 3D-printed polypropylene capsule-containing copper(II) loaded onto polystyrene-supported 1,5,7-triazabicyclo[4.4.0]dec-5-ene (PS-TBD) allowed the rapid synthesis of diverse substituted 1-([1,1'-biphenyl]-4-yl)-1H-1,2,3-triazoles. The procedure is based on the Chan-Lam azidation/copper alkyne-azide cycloaddition/Suzuki reaction strategy in the solution phase. This catalytic system enabled the efficient assembly of the final compounds in high yields without the need for special additives or intermediate isolation. The monolithic catalyst-containing immobilized palladium species was synthesized by surface chemical modification of a 3D-printed silica monolith using a soluble polyimide resin as a key reagent, thus creating an extremely robust composite. All three immobilized catalysts described here were easily recovered and reused in numerous cycles. This work exemplifies the role of 3D printing in the design and manufacture of devices for compartmented multicatalytic systems to carry out complex one-pot transformations.

Structural investigation of chemically synthesized ferrite magnetic nanomaterials

In recent times, interest in ferrite magnetic nanomaterials has considerably grown, mainly due to their highly promising medical and biological applications. Spinel ferrite powder samples, with high heat generation abilities in AC magnetic fields, were studied for their application to the hyperthermia treatment of cancer tumors. These properties of ferrites strongly depend on their chemical composition, ion distribution between crystallographic positions, magnetic structure and method of preparation. In this study, crystal and magnetic structures of several magnetic spinels were investigated by neutron diffraction. The explanation of the mechanism triggering the heat generation ability in the magnetic materials, and the electronic and magnetic states of ferrite-spinel type structures, were theoretically defined by a first-principles method.Ferrites with the composition of CuxMg1-xFe2O4 have been investigated as a heat generating magnetic nanomaterial. Atomic fraction of copper in ferrite was varied between 0 and 100% (that is, x between 0 and 1.0 with 0.2 steps), with the copper dope limit corresponding to appear a tetragonal phase.

Aging kinetics of 17-4 PH stainless steel

The influence of aging condition and the precipitation kinetics of 17-4 PH stainless steel (AISI 630) were studied in this paper. The effect of aging temperature and time in terms of tempering parameter on the strengthening behavior of this steel was modeled and analyzed by means of artificial neural networks (ANNs). The hardening, overaging and softening behaviors in accordance to aging reactions (precipitation and coarsening of Cu, recovery, and reversion of martensite to austenite) were determined from this ANN model. Moreover, Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis were applied to characterize precipitation kinetics of this martensitic age hardenable alloy. Time exponents (0.465 on average) were within the range reported for maraging steels. The activation energy for precipitation reaction was determined as 262 kJmol −1 which is consistent with the activation energy for diffusion of copper in ferrite. Furthermore, precipitation rate showed exponential dependence on aging temperature.

The effect of copper on passivity and corrosion behaviour of ferritic and ferritic–austenitic stainless steels

The paper presents investigations of the influence of copper as an alloying element on the structure and on the passive behaviour of ferritic Fe–18%Cr and duplex ferritic–austenitic Fe–24%Cr–6%Ni–3%Mo cast alloys. Copper dissolved in the solid solution (austenite) does not show detrimental effect on the stability of a passive film. The solubility of copper in ferrite is lower than in austenite and therefore the ε-phase can be precipitated during thermal treatment (500–600°C). Ferritic alloy containing high copper content (1.58%Cu) shows precipitation of the ε-phase already in cast form (without sensitisation). In duplex ferritic–austenitic steels, the precipitation of the ε-phase in ferrite occurs during the sensitisation in a temperature range 500–600°C. The presence of the ε-phase stimulates pitting corrosion of ferrite. Electrochemical measurements of the passive behaviour of investigated materials show that the alloys containing precipitates of the the ε-phase undergo pitting corrosion in 1 M H2SO4–1 M NaCl. Thermal treatment dissolving the ε-phase increases the resistance of alloys to local attack. Our experiments show that the increase of copper content in ferritic alloys increases also the tendency to chromium segregation at grain boundaries and thus the tendency to intergranular corrosion of cast alloys.

On the ferrite-austenite equilibrium in the Fe-Cu system

The thermodynamics of ferrite containing dissolved copper is analyzed theoretically, taking into account the effect of copper on the Curie temperature. By combination with experimental information on the solubility of copper in austenite, this model is used to predict the solubility of copper in ferrite. The result shows good agreement with experimental data but indicates that the data should be extrapolated in a manner different from that which has been previously suggested. The effects of copper and cobalt on the relative stability of the α and γ phases in iron-rich alloys are compared. It is concluded that their difference is mainly caused by the difference in their effects on the Curie temperature of α-iron.