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Chalcostibite copper antimony sulfide (CuSbS2) micro- and nanoparticles with a different shape and size have been prepared by a new approach to hot injection route. In this method, sulfur in oleylamine (OLA) is employed as a sulfonating agent providing a simple route to control the shape and size of the particles, which enables the optimization of CuSbS2 for a variety of applications. The sulfur to metallic precursor ratio appears to be one of the most effective parameters along with the temperature and time for controlling the size and morphology of the particles. The growth mechanism study shows in addition to the CuSbS2 phase the presence of not previously observed intermediate phases (stibnite (Sb2S3) and famatinite (Cu3SbS4)) at the initial stage of the reaction. By increasing the ratio of sulfur to copper and antimony, wider and thinner CuSbS2 particles are obtained. The particles have nanoplate and nanosheet morphology with a good shape and size uniformity. Coalescence of very thin nanosheets occurs with increasing reaction time eventually leading to formation of thicker particles which can be called nanobricks. Band gap determinations demonstrate that the obtained CuSbS2 particles have both direct (1.51–1.57 eV) and indirect (1.44–1.51 eV) bandgaps. Transmission Electron Microscopy (TEM) studies revealed that the preferred growth directions are along the basis axes of the unit cell ( [ 100 ] and [ 010 ] ). Optical and structural properties of the obtained CuSbS2 particles are indicative for their great potential in different generations of solar cells and supercapacitor applications.

In powder technologies such as sintering, 3-D printing, and thermal spraying, the characteristics of the powders are of uttermost importance. This holds for composition as well as for phase and grain structure. In this work, we characterize argon gas atomized Cr25.2Fe24.8Ni25.5Mn24.5 high entropy alloy powder, which is a material of high interest for applications requiring high strength and radiation resistance. The microstructure of gas atomized particles at different class sizes is characterized and the powder properties are determined by nanoindentation and magnetic measurements. The atomized particles have a smooth spherical shape with a fine surface pattern. The composition and phase structure as well as hardness and magnetic properties are particle size dependent, i.e., depend on cooling rate during atomization. The phase structure of the atomized powder is nearly single FCC phase with a small amount of BCC phase, the amount of which increased with the decreasing powder particle size. Average nanohardness determined from nanoindentation of particle class sizes

Two double dispersion composites were prepared by pulsed electric current sintering (PECS) from two powders on Ni–Mn–Ga–Co/WC–Co system. Composite 1 consists of 90 vol% WC–12Co and 10 vol% of non-modulated Ni–Mn–Ga–Co martensite and Composite 2 of 18 vol% of WC–12Co and 82 vol% of 10 M Ni–Mn–Ga–Co martensite. Damping capabilities of both composites were studied with DMA and cavitation erosion resistance tests. Both composites show promise as candidates as damping element materials when high hardness and wear resistance is required but Composite 2 had a higher damping capability. The high damping ability of composites are proposed to be derived from the combined effect of energy dissipation by twin boundary movement in the Ni–Mn–Ga matrix combined with the high hardness and wear resistance arising from the tungsten carbides.

Highly mobile twin boundaries allow straining of the 10M Ni–Mn–Ga martensite single crystals with low as 0.15 MPa uniaxial stresses. This is clearly lower than what is possible to magnetically generate in this structure. Therefore, this material can be used for magnetically controlled actuation. In cyclic deformation occurring by twin variant reorientation, fatigue life up to 2 × 10 9 cycles has been demonstrated without decrease of the magnetic-field-induced strain or without failure of the specimen. However, the actuation behavior can be strongly impaired by unfavorable twin variant configuration or surface constraints which decrease the twin mobility and increase the twinning stress. In the present work, the surface properties of the 10M Ni–Mn–Ga are studied in details. The existence of an ultra-thin surface layer having chemical composition different from the bulk crystal is established with the XPS analysis. The influence of this layer on the nano-mechanical properties of the surface is investigated using instrumented nanoindentation both on electropolished crystals and crystals where surface deformation has been introduced by mechanical polishing. The results show that the surface layer appears both in the electropolished and mechanically polished surface. However, the nano-mechanical properties of the surface are distinctly different in the two cases. In the case of electropolished surface essentially elastic loading occurs first followed by a notable pop-in of the indenter, while in the case of mechanically polished surface minor or no pop-in is observed. This behavior is attributed to the differences of the initiation of plastic deformation in the two types of surfaces. The contribution of the layer to the performance and actuation properties of the material is discussed. © 2012 Elsevier B.V. All rights reserved.

Ni–Mn–Ga alloys were compacted using pulsed electric current sintering (PECS) at 850–875 °C (50 MPa, 8 min) of flake-like powders made from the rapidly quenched melt-spun ribbons. Two kinds of ribbons were used: one made with a relatively slow wheel speed (6 m/s; average grain size ∼14 μm), and another with a faster wheel speed (23 m/s; average grain size ∼5 μm). Both sets of flake-like powders consisted of a mixture of non-modulated martensite (NM) and seven-layered modulated martensite (7M) structure. The amount of NM was greater in the slower speed material, while the other one exhibited mostly the 7M structure. These crystal structures were inherited by the sintered samples. In the compacts having the NM structure the multi-step martensitic reaction overlapped with the magnetic transition, and the Curie temperatures during heating and cooling differed from each other. In the compacts having mainly 7M structure the Curie point was about 100 °C and the martensitic transition took place in the paramagnetic state, while the intermartensitic one occurred in the region of 60–85 °C. This material demonstrated good magnetic properties and saturation magnetization, at best ∼50 emu/g. Mechanical properties of the compacts were good, and comparable to those of the polycrystalline Ni–Mn–Ga samples in compression.