Investigation of crystal structure formation by electropulse treatment of amorphous Ti50Ni25Cu25 alloy ribbons

The study of the effect of electropulse treatment with a variable duration on the crystallization processes and the structure of a amorphous TiNiCu alloy with 25 at.% Cu in comparison with isothermal annealing and heating at a constant speed was carried out. The alloy was fabricated by rapid-quenching from the liquid state (melt spinning technique) at the cooling rate of the melt of about 106 °C/s in the form of a ribbon with a thickness of 28 μm with a surface crystal layer with a thickness of about 2-3 μm. To remove the crystal layer, the method of double-sided electrochemical polishing was used. The studies were carried out by methods of differential scanning calorimetry, metallography and scanning electron microscopy. It was established that the formation of the crystalline phase in the electropulse treatment of the amorphous ribbon occurs from the surface to the inner part due to the predominant formation and growth of columnar crystals with subsequent nucleation and growth of crystals in the rest of the ribbon.

Thermal and Mechanical Characterization of Drawn Polypropylene Fibres

The main objective of this work was to investigate the effect of different cellulose (CEL) content and the draw ratio on the thermal and mechanical properties of drawn polypropylene (PP) fibres. The modification of PP fibres during their production can helps to prepare PP fibres with improved properties, guarantees new opportunities for the expansion of an assortment of PP fibres in the clothing and domestic textile industries. The modified PP/CEL fibres were prepared from PP pellets and PP/cellulose masterbatch via the melt spinning technique at 260 °C followed by drawing for various draw ratios in the company Chemosvit, Fibrochem a. s. (Svit, Slovakia). Differential scanning calorimetry (DSC) was used to evaluate the thermal properties of PP fibres. The mechanical properties (tenacity and elongation at break and modulus of elasticity) and low cycle loading of modified PP fibres were also studied. The obtained experimental results of drawn PP/CEL fibres were compared with neat PP fibre prepared under the same technological conditions. Cellulose had a minimal effect on the melting temperatures of fibres and increased of the PP crystallization temperatures in comparison with the neat drawn PP fibre. The limited decrease of mechanical properties of prepared fibres were observed, but the decreases do not influence on the fibres commercial use.

Synthesis and Characterization of Mnbi Magnetic Alloy via Two Different Processing Routes

Manganese bismuth alloy has gained importance due to its rare earth free elements, positive temperature coefficient and unique magnetic properties. Low temperature phase (LTP) MnBi was successfully prepared by arc melting with subsequent heat treatments and melt spinning technique followed by heat treatment for different durations. LTP MnBi formation was confirmed using XRD analysis and microstructural characterization of the samples was done using field emission scanning electron microscope. MnBi with greater LTP amount was formed by melt spinning route when compared with its counter arc melted one. Magnetic energy density of LTP MnBi formed by melt spinning technique with different heat treatment time was studied.

Microstructure and Catalytic Activity of Melt Spun Al-Cu-Fe Ribbons

The Al65Cu20Fe15 (in at.%) rapidly solidified ribbon in the form of brittle flakes was produced by melt-spinning technique. It consists the cell or dendrites of the icosahedral quasicrystalline I-phase surrounded by copper rich cubic τ-Al(Cu, Fe). The pulverized ribbon (fraction <32 μm) was subjected to NaBH4 or 20% aqueous NaOH treatment, which led to the formation of oxide in the form of thin flakes at the outer layer of the powder particles. Test of the catalytic properties of the as spun ribbon and powder before and after treatment was made in the reaction of phenylacetylene hydrogenation. It was shown that for as received ribbon, even at very mild conditions (60 °C, H2 pressure of 5 bar), 40% of phenylacetylene was converted to hydrogenation products with 0.7 styrene/ethylbenzene ratio. The use of pulverized ribbon resulted in improvement of activity, with the same ratio of reaction products. The effect of treatment with NaBH4 led to improvement of the catalyst activity, while strongly alkaline solution of NaOH worsened significantly the catalytic activity, but improved selectivity to styrene (styrene/ethylbenzene=1.2).

The Influence of Heat Treatment on the Phase Structure of the Nanocrystalline (Nd10Fe67B23)95Nb5 Alloy Ribbons

The main goal of present paper was to study of phase composition of nanocrystalline (Nd10Fe67B23)95Nb5 ribbons prepared by melt-spinning technique with different velocity of the copper wheel. Samples in the as-cast state obtained using speed 5 and 10 m/s had nanocrystalline structure. In case of samples prepared by with speed of copper Wheel 15 and 35 m/s were fully amorphous. In the DSC curve, the two minima corresponding to crystallization of the Nd2Fe23B3 and Nd2Fe14B phases were detected. The coexistence of three phases: Nd2Fe14B, Nd2Fe23B3 and Nd1+εFe4B4 were detected. Higher temperatures of annealing caused crystallization of α-Fe phase. The XRD results were confirmed by the Mössbauer studies. Keywords: hard magnetic materials, phase structure, Mössabuer spectroscopy

Reliable Sn–Ag–Cu lead-free melt-spun material required for high-performance applications

This study investigates the structural, mechanical, thermal and electrical properties of B-1 JINHU, EDSYN SAC5250, and S.S.M-1 commercial materials, which have been manufactured at China, Malaysia, and Germany, respectively. The commercial materials have been compared with the measurements of Sn–Ag–Cu (SAC) melt-spun materials that are only indicative of what can be expected for the solder application, where the solder will have quite different properties from the melt-spun materials due to the effects of melt-spinning technique. Adding Cu to the eutectic Sn–Ag melt-spun material with 0.3 wt.% significantly improves its electrical and mechanical properties to serve efficiently under high strain rate applications. The formed Cu3Sn Intermetallic compound (IMC) offers potential benefits, like high strength, good plasticity, consequently, high performance through a lack of dislocations and microvoids. The results showed that adding 0.3 wt.% of Cu has improved the creep resistance and delayed the fracture point, comparing with other additions and commercial solders. The tensile results showed some improvements in 39.3% tensile strength (25.419 MPa), 376% toughness (7737.220 J/m3), 254% electrical resistivity (1.849 × 10−7 Ω · m) and 255% thermal conductivity (39.911 w · m−1 · k−1) when compared with the tensile strength (18.24 MPa), toughness (1625.340 J/m3), electrical resistivity (6.56 × 10−7 Ω · m) and thermal conductivity (11.250 w · m−1 · k−1) of EDSYN SAC5250 material. On the other hand, the Sn93.5–Ag3.5–Cu3 melt-spun solder works well under the harsh thermal environments such as the circuits located under the automobiles’ hood and aerospace applications. Thus, it can be concluded that the melt-spinning technique can produce SAC melt-spun materials that can outperform the B-1 JINHU, EDSYN SAC5250 and S.S.M-1 materials mechanically, thermally and electrically.