This study compares five Si-Me infiltration coatings, Si:Mo (1:4), Si:Ti (1:1), Si:Zr (1:5), Si:Ta (1:1), and Si:W (1:5), deposited on C/C sonotrodes for ultrasonic atomization of CuSn8. The coatings were evaluated in terms of phase constitution, microstructure, wettability, nanoindentation response, and powder-production performance. XRD showed that the coatings formed distinct multiphase reaction layers, with Si:Ta (1:1) being the most silicide-dominated system, while the other coatings contained carbide or silicide-carbide phases. Metallization strongly improved the surface wettability of C/C, especially for Si:Zr (1:5) and Si:W (1:5). Nanoindentation indicated the most favorable H/E* and H3/E*2 descriptors for Si:W (1:5) and Si:Mo (1:4). All coatings enabled high powder yields in single-run atomization tests, while apparent differences in particle-size distribution were observed among the coating conditions. Overall, the results show that coating selection for ultrasonic atomization should combine phase constitution, surface-state descriptors, near-surface mechanical response, layer retention, and process performance. Within the investigated conditions and the limitation of single-run atomization experiments, Si:W (1:5) emerged as the most promising and best-balanced coating candidate, while Si:Ta (1:1) and Si:Mo (1:4) remained relevant alternatives.

This paper describes a strategy for creating highly oriented crystalline-amorphous composites using the laser powder bed fusion (LPBF) process. The strategy involves using a novel two-stage melting approach and ultra-high-pressure hot isostatic pressing (HIP) on well-known AMZ4 (Zr59.3Cu28.8Al10.4Nb1.5) and equiatomic CuZr amorphous alloys. The experiments demonstrate that by the fine-tuning laser parameters, allowed to obtain parts with purely amorphous material and to create geometry-specific microstructural design composites based on laminate amorphous-crystalline structure. This approach also provides novel opportunities for nonequilibrium phase distribution design by controlling local crystallization in the heat-affected zone (HAZ) and avoiding heat accumulation. Additionally, the porous amorphous material can be densified without crystallization using HIP at a temperature near the supercooled liquid region. The distribution of the crystalline phase created during LPBF and crystallization on pre-induced nuclei during HIP was proven to be a critical factor for composite properties. Wear and bending tests reveal the influence of crystalline-amorphous layers orientation on mechanical properties. The functional demonstrators were manufactured to show the possibilities in the design for additive manufacturing (DfAM) with a microstructure-designed composites.

An effective and complete processing route for the recycling of sintered Nd-Fe-B scrap magnets was proposed. Sintered Nd-Fe-B magnets were subjected to the Hydrogen Decrepitation (HD) process at various temperatures in the range of 50-300 degrees C, at two different pressures, 50 kPa and 200 kPa, followed by vacuum dehydrogenation in the range of 720-820 degrees C. The structure refinement efficiency and magnetic properties of the powders obtained were characterized. Low hydrogen pressure (50 kPa) was found to increase the magnetic properties at each temperature for all powder fractions. It was also shown that particle refinement occurs at low (50 degrees C, 100 degrees C) temperatures for low (50 kPa) pressure and higher temperatures (200 degrees C, 300 degrees C) for high pressure (200 kPa), respectively. High pressure also accelerates the initialization of the HD process at each temperature. No correlation was found between hydrogenation temperature and magnetic properties of the powders, except for the small increase in coercivity increase with growing temperature. The coarse fraction (400-500 mu m) was found to have the highest magnetic properties for almost each HD process. The best magnetic properties H-ci = 497 kA/m, B-r = 1.1 T, and (BH)(max) = 121 kJ/m(3) were obtained for hydrogenation at a temperature of 50 degrees C, pressure 50 kPa and dehydrogenation at 780 degrees C.

Shear thickening fluid (STF) -often referred to as dilatant fluid -is a non-Newtonian suspension of a solid component in a liquid carrier, with an unique ability to dissipate the impact energy.The viscosity of STFs increases abruptly with a growing shear rate.Beyond the critical value of the shear rate, the fluid transforms from a liquid-like to a solid-like state.High-grade dilatant fluids, besides the appropriate rheological properties and protecting capability, have to present high structural stability.The unique properties of the STFs make them suitable for human body protection.The STFs provide lots of opportunities for creating composites with great energy absorption ability, for example, in smart armors or sports protectors.The properties of shear thickening fluid, modified by the addition of multiwalled carbon nanotubes (MWCNT), were characterized.The addition of a small amount of carbon nanotubes to shear thickening fluid leads to an increase of maximal viscosity, from 2128 to 12213 Pa•s.To show the differences between various compositions, the microstructures of fluids were observed by scanning electron microscopy (SEM).The pronounced influence of the MWCNT on the ability of impact force absorption was noticed.The protective structure containing 55 and 0.25 vol.% of fumed silica and MWCNT, respectively, is able to absorb up to 74 % of impact force.

A new powder production method has been developed to speed up the search for novel alloys for additive manufacturing. The technique involves an ultrasonically agitated cold crucible installed at the top of a 20 kHz ultrasonic sonotrode. The material is melted with an electric arc and undergoes pulverization with standing wave vibrations. Several different alloys in various forms, including noble and metallic glass alloys, were chosen to test the process. The atomized particles showed exceptional sphericity, while powder output suitable for additive manufacturing reached up to 60%. The AMZ4 metallic glass powder remained amorphous below the 50 μm fraction, while tungsten addition led to crystallization in each fraction. Minor contamination and high Mn and Zn evaporation, especially in the finest particles, was observed in atomized powders. The innovative ultrasonic atomization method appears as a promising tool for material scientists to develop powders with tailored chemical composition, size and structure.

The GeniCore Upgraded Field Assisted Sintering Technology U-FAST was applied to the sintering of a commercial Zr-based bulk metallic glass powder AMZ4. The XRD, SEM and DSC analysis of the sintered compacts showed the benefit of the U-FAST method as an enabler for the production of fully amorphous samples with 100% relative density when sintering at 420 °C/480 s (693 K/480 s) and 440 °C/ 60 s (713 K/480 s). The hardness values for fully amorphous samples, over HV1 519, surpass cast materials and 1625 MPa compressive strengths are comparable to commercial cast products. The advantage of the U-FAST technology in this work is attributed to the high heating and cooling rates inherent to ultra-short pulses, which allow to maintain metastable structures and achieve better temperature control during the process. Increasing sintering temperature and time led to the crystallization of the materials. The geometry and material of the dies and punch determine the thermal inertia and pressure distribution inside the compacts, thus affecting the properties of the near net shape NNS compacts made using the U-FAST device.

Synthesis and characterization of composite shear thickening fluids (STFs) containing carbon nanofillers are presented. Shear thickening fluids have attracted particular scientific and technological interest due to their unique ability to abruptly increase viscosity in the case of a sudden impact. The fluids have been developed as a potential component of products with high energy absorbing efficiency. This study reports on the rheological behavior, stability, and microstructure of the STFs modified with the following carbon nanofillers: multi-walled carbon nanotubes, reduced graphene oxide, graphene oxide, and carbon black. In the current experiment, the basic STF was made as a suspension of silica particles with a diameter of 500 nm in polypropylene glycol and with a molar mass of 2000 g/mol. The STF was modified with carbon nanofillers in the following proportions: 0.05, 0.15, and 0.25 vol.%. The addition of the carbon nanofillers modified the rheological behavior and impact absorption ability; for the STF containing 0.25 vol.% of carbon nanotubes, an increase of force absorption up to 12% was observed.

Effect of Pb addition on magnetocaloric properties of Ni50Mn18,75Cu6,25-aPbaGa25 (a = 1, 2, 3, 4, 5) alloys was investigated experimentally. The magnetic measurements conducted at low field of 4 kA/m showed that addition of Pb led to separation of the both transformation temperatures and significantly shifted the structural transition effect towards lower temperatures as well as increased the Curie temperature. The analysis of isothermal magnetic curves allowed for the calculation of magnetic entropy change (Delta S-M). Although the peak values of vertical bar Delta S-M vertical bar for alloys containing 4 and 5 at.% Pb, similar to 3 J/(kg*K) and similar to 1.5 J/(kg*K) respectively, are low they stretch over the structural transformation and Curie temperature, and are at least 30 K wide at half maximum height.

The properties of shear thickening fluid (STF), based on polypropylene glycol and amorphous silica, modified by the addition of multiwalled carbon nanotubes (MWCNTs), were studied. The STF’s viscosity increases abruptly during impact tests. The addition of a small amount of carbon nanotubes (CNTs) to the STF, leads to an increase of the maximal viscosity from 2128 to 12,213 Pa$$\cdot $$s. To show the differences between various compositions, the microstructures of fluids were observed by scanning electron microscopy. A pronounced influence of the CNTs on the ability of impact force absorption was noticed. The protective structure containing 55 and 0.25 vol% of fumed silica and CNTs, respectively, is able to absorb up to 74% of impact force.

Rheological behavior and structural stability of shear thickening fluids (STFs) based on amorphous silica KE-P50 (500-600 nm) and polypropylene glycol, with molar mass 2000 g mol(-1), were studied. The static and dynamic rheological measurements were performed using rheometer ARES and stability tests were carried out using the static multiple light scattering (S-MLS) method. The preliminary tests were performed for the STFs having 50-55 vol% of silica and the detailed studies were carried out for two fluids, with 50 and 53 vol% of silica, respectively. All the STFs studied exhibit shear thickening properties. Both, the zero-shear-viscosities and maximal viscosities increase with growing silica content. For the shear rates studied the viscous component of the shear modulus dominates over the elastic one. S-MLS tests showed that both the suspensions studied exhibit excellent stability over the 8 days of the test. The synthesized STFs can be used as a component of flexible energy absorbing and protecting structures.

Acoustic Emission Testing (AT) was applied to monitor the Hydrogen Decrepitation (HD) process for two different NdFeB-type materials: sintered NdFeB magnet and annealed NdFeB ingot alloy. Acoustic signals of clearly different characteristics were acquired for these two materials, indicating different course of the HD process. Acoustic waves of high signal strength and high peak amplitude were generated for the sintered NdFeB magnet whereas acoustic signals of low energy and low intensity were registered for the annealed NdFeB alloy. These findings were supported by real-time visual observation of the HD process. The sintered NdFeB magnet decrepitates rapidly and its particles spatter for a longer distance comparing to the ingot NdFeB alloy. Different behavior of the investigated materials can be explained in relation to their structural properties and manufacturing history. Fine microstructure, homogenously distributed thin layer of the Nd-rich grain boundary phase and stress accumulated after fabrication process can be responsible for more intense characteristic of the HD process in case of the sintered NdFeB magnets.

The paper presents a new approach to selective laser melting (SLM) of alloys with low glass-forming ability and the basics of microstructure evolution during SLM of iron-based metallic glasses. After extensive parameters optimization, a novel scanning strategy, involving two-step melting, comprising preliminary laser melting, followed by short-pulse amorphization, has been introduced to maximize the glassy phase fraction and ensure good magnetic properties. Single melted samples show poor amorphization with well separated amorphous regions and coercivity of 1032 A/m. Second melting increased the glassy phase content by over an order of magnitude - up to 89.6% and reduced coercive force over four-times to 238 A/m. X-ray diffractions show significant difference between, arising from melt, disordered Fe(Si) phase and devitrified, ordered Fe3Si. Coexistence of those phases has been shown in heat affected zone by electron diffraction. Beneficial effect of the novel remelting strategy has been explained on the basis of restricted crystallization in heat-affected zone and reduction of sample overheating, by application of the Point-Random strategy.

Synthesis and characterization of a novel, multifunctional, solvent-free room-temperature liquid based on alkylated double-decker lutetium(III) phthalocyanine (Pc2 Lu) are described. Lowering of the melting point and viscosity of intrinsically solid Pc2 Lu compounds has been achieved through the attachment of flexible, bulky, and long branched-alkyl chains, that is, thio-2-octyldodecyl, to the periphery of the Pc2 Lu unit. The embedded Pc2 Lu unit maintains its inherent molecular functions, such as spin-active nature and electrochromic behavior in the liquid state. Comparison of the properties with a solid-like Pc2 Lu derivative, functionalized with shorter alkyl chains, that is, thio-2-ethylhexyl, underlines the importance of the hampering effect on the π-π interactions of neighboring Pc2 Lu molecules by bulkier and longer branched-alkyl chains. This study could possibly pave the way for novel multifunctional liquids whose spin-activities are associated with their rheological or optoelectronic properties.

Bridgman method with stationary crucible was used to grow NiMnCuGa single crystal. Microstructure observations, as well as XRD pattern, revealed a presence of martensitic structure at room temperature. Crystal structure was determined as a non-modulated tetragonal martensite. The phase transition occurred at 296 K and 290 K on heating and cooling, respectively. Magnetic entropy change (DSM) reached a peak value of -9.86 J/kgK at the field of 1520 kA/m. Refrigerant capacity (RC), calculated at FWHM of the DSM peak, reached a value of 28.5 J/kg. Directly measured adiabatic temperature change (Delta T-ad) spread over 51 K range and its maximum value reached 0.23 K at 1520 kA/m field. (C) 2018 Elsevier B.V. All rights reserved.

The elastomeric anti-trauma pad (EA-TP) based on shear thickening fluid (STF) has been developed. Dynamic oscillatory shear experiment was conducted at constant strain amplitude of 5%. STF composed of 25% of volume fraction of 7 nm Fumed Silica, dispersed in polypropylene glycol with molar mass 400 gmol−1 shows elastic properties in entire investigated range of the frequency. Ballistic tests of EA-TP with 7.62 mm × 39 mm PS bullets were performed according to the PN-V-87000:2011 standard. The studies revealed about 60% reduction of the average backface signature depth (BSD) for the EA-TP, when compared to the nowadays commonly used soft insert. The ATR-FTIR analysis confirmed slight impact of the elevated temperature and air (oxygen) on the chemical degradation of the EA-TP surface. The UV-VIS spectroscopy has allowed to notice colour deviation of the aged samples towards green and yellow, as well as lack of dye resistance to accelerated aging process. Thermographic analysis has shown no visible changes of the EA-TP surface and sub-surface during accelerated aging process. The aforementioned small changes on the surface of EA-TP did not affect the ballistic properties of composite armour. EA-TP insert maintains ballistic properties after accelerated aging process which was simulating the period of 6 years according to ASTM F1980 – 07:2002 standard.

Hydrostatic extrusion is a modern method of shaping material microstructure and properties. Hydrostatic extrusion can also be successfully used for consolidation of hard magnetic powders. The effect of extrusion temperature, within the range of 700-800 degrees C, on the magnetic properties of the bulk, final product was studied. A commercial MQU-F42 powder, dedicated to hot pressing, was placed in copper capsules and initially cold compacted up to 60% of the theoretical density. Subsequently, the billet was heated in an oven to temperatures 700 and 800 degrees C, respectively and subjected to hydrostatic extrusion. The extruded product had a form of a copper rod, with the Nd-Fe-B core, having 96% of theoretical density (true strain 1.85 after extrusion at 800 degrees C). The extrusion process led to deterioration of the coercivity, for which coarsening of the Nd2Fe14B grains was blamed. In order to prove this hypothesis, the starting powder was annealed in a temperature range of 550-900 degrees C for various times. The crystallite size, measured after annealing by the X-ray diffraction method, showed that with extension of time and elevation of the temperature the crystallite size increases, however the dominating parameter is the temperature. Correlation of the crystallite size with temperature indicates that when the crystallites are larger than 80 nm the magnetic properties dramatically decrease. Additionally, after HE at 800 degrees C micrometric size Nd-rich phase appear in the microstructure. The Nd is squeezed from the grain boundary of the Nd2Fe14B phase leading to non-isolated grains, which also contributes to the deterioration of the coercivity.

Thermodynamic assessment of Fe-B system, including phase diagram, Gibbs energy, enthalpy, heat capacity and activity, was performed in the ThermoCalc software ver.4.1 (Sweden).Two databases were used: the commercial SSOL5 database for solid solutions (substitutional approach) and the USER made database based on work of T. Van Ro mpaey et al. (intersticial approach).Results obtained were c ompared with experimental data gathered from work of M. Van Ende et al.In low boron regime the curve of the Fe -B phase diagram is represented more reliable in the USER database.However, temperatures of the phase transformations are calculated with more accuracy in the SSOL5 database.For boron content higher than 0.3 mole fraction phase transformation temperatures are better assessed in the USER database, except for melting point of the Fe 2 B phase.Gibbs energy, enthalpy and heat capacity of the FeB and t he Fe 2 B are difficult to evaluate because experimental data are spread and inaccurate.Activities of iron and boron in liquid Fe -B alloy, calculated at selected temperatures, are almost identical for both databases.paramount importance.

The issue of energy absorption during impact is present in various aspects of life. The possibility of dissipating unwanted energy gives huge opportunities for a variety applications such as helmets, car bumpers, smart body armours and protective pads. Nevertheless, there are numerous technical problems with achieving a compromise between good energy absorption efficiency and other important properties such as flexibility, weight and thickness. The article describes a study of composite structures based on shear thickening fluids (STF) and auxetic foams. The composites are developed as a potential component of products with high energy absorbing efficiency. The study reports on the rheological behavior of STF and force absorbing properties of the manufactured composites. In the experiment, two types of STF and eleven types of auxetic foams were used. Force absorbing tests for the produced samples were performed by dropping an impactor with the energy of 5 J. It was proved that the addition of STF to the auxetic foams increases the force absorbing efficiency.

Sintered Nd-Fe-B magnets, dismantled by the P.P.H.U. Polblume company from scrap hard disc drives and medical device, were thermally demagnetized and analyzed in terms of their chemical composition, structure and magnetic properties. Magnets from hard disc drives drives had a magnetic structure of two opposite poles in a plane of a magnet and were covered with a nickel coating (around 50 mu m in thick), which however was often discontinuous and deeply scratched. The majority of the magnets were partially destroyed (broken or corroded). The magnet from hard disc drives were basically made of iron (65 +/- 1 wt%) and neodymium (30 +/- 2 wt%) however, they also included alloying elements such as Co (1-2.5 wt%), Dy (0-1 wt%) or Pr (0-5 wt%). The magnets from medical device consisted only of iron (65 +/- 1 wt%) and neodymium (34 +/- 1 wt%). Magnets of both kinds were textured thus their XRD patterns were amended. Diffraction patterns, typical for the Nd2Fe14B (phi) phase, were achieved after mechanical crushing of the bulk magnets. A regular X-ray diffraction pattern was achieved after mechanical crushing of the magnets. The microstructure of both types of the magnets, observed by scanning electron microscopy, consisted of grey grains of a Nd2Fe14B (phi) phase and a Nd-rich grain boundary phase. The magnets from hard disc drives exhibited excellent magnetic properties and anisotropy: maximum energy product above 300 kJ/m(3), remanence around 1.4 T and coercivity around 1000 kA/m, slightly varying between each magnet. Magnetic properties of medical magnet were only a little worse: maximum energy product above 200 kJ/m(3), remanence around 1.1 T and coercivity around 900 kA/m. Hydrogen disproportionation phase diagrams (temperature vs. pressure) were constructed for both kinds of the magnets, revealing possible conditions for the hydrogenation, disproportionation, desorption and recombination reaction.

Studies done on recycled products gained from computer boards have been presented. Alloys fabricated by melting of computer boards were investigated in detail. It was found that the alloy is segregated into two regions - copper and iron rich, in which other alloying elements, forming either solid solutions or intermetallic phases, are dissolved. Scale from melting and sediment from etching metals in hydrochloric acid were also studied. In the scale fluxing agents and residual of metals were gathered, whereas in the sediment some amount of noble metals was detected. Microscopic investigations and chemical composition measurements were performed on alloys from melted boards as well as on the scale and the sediment.