Papers by Keyword: Rhenium

Abstract: NiTi alloy has desired engineering properties with many applications, such as biomedical, aerospace, automotive, etc, where several researchers have investigated the development of ternary and quaternary alloying of NiTi to further enhance its performance for demanding technological applications. However, there are limited studies on the effects and synergy of Re and Mo on the nanomechanical properties of NiTi alloy, despite the highly recommended effect of Re on the mechanical properties of Ni-based superalloys. Therefore, this study bridged this gap by developing NiTi-Re-Mo alloy via the spark plasma sintering technique and investigating its nanomechanical properties in relation to NiTi, NiTi-Re, and NiTi-Mo alloys. It was noted that NiTi-Re-Mo has better nanomechanical responses than other developed NiTi-based alloys. For instance, the hardness and elastic modulus of NiTi-Mo-Re increased to about 28236.7 MPa and 483.4 GPa from 4460.7 MPa and 122.5 GPa for NiTi alloy, respectively. These significant increments were credited to the synergy effect of Re and Mo, the solution and hard phase precipitation strengthening of the NiTi system, which also contributed to the reduction of dislocations and improved mechanical locking of the NiTi system. This makes the alloy desirable for high mechanical strength applications.

Abstract: Electric spark of alloying – ESA – from the standpoint of materialogy, a new stage in the development of the materials science, is a method of surface hardening that refers to technologies meeting the new development vector of the materials science, including its most important sections – surface materialogy. As an anode material, an unconventional material for the electric-spark coating method (ESA) - rhenium is of practical interest for creating protective and hardening coatings. The results of studies of the formation modes by the method of ESA are given on the surface of steel grade 35 of the alloyed layer and its properties using the anodic material from rhenium is shown. The kinetics of the doped layer formation depending on the ESD regimes, their justification is shown. It is established that with an increase of the frequency of discharge pulses in the range of 1600>f_cps>20 Hz, a trend to increase the thickness of the AL h_av.AL is observed, and with an increase in energy 1.8>E>0.11 J, on the contrary, there is a trend of its decrease; the latter is associated with a decrease of the pulses frequency with the increase of energy. The obtained series of the efficiency of the ESA process make it possible to predict the achievement of the required parameters of the doped layer using Re as the anode material.

Abstract: Ni-based single crystal superalloy turbine blades have excellent mechanical strength and resistance to corrosion and oxidation due to a uniformly distributed gamma prime phase in a gamma matrix. However, defect grains have been often found on the surface of turbine blades after manufacturing, which can be potential sites of crack initiation. In this study, several different types of surface defect grains formed in third generation Ni-based single crystal turbine blades, such as stray grains, freckle chain grains, equiax grains, and a new grain formed in surface scale, had been investigated. The grain boundary regions were observed by high resolution electron microscopy. Although the formation mechanism of each grain defect is different, secondary phases, such as rhenium-rich particles, have been always found in each grain boundary. In addition, depending on the existence of the secondary phases as well as the size of defect grains, different microstructures were observed even in the same defect grain boundary. Finally, the observed results suggest that if there is any boundary region in a turbine blade, secondary phases, such as Re-rich particles, can be found.

Abstract: In spite of selectivity of platinum and rhenium stripping voltammetry analysis techniques, it is very difficult to identify them in the presence of other metals. This manuscript reports on the stripping voltammetric determination of platinum and rhenium in the presence of other metals. The effect of accompanying elements on the electrochemical oxidation processes of platinum and rhenium has been described. It has been shown that it is possible voltammetric determination of platinum and rhenium after removal of interfering matrix components of mineral raw materials at the stage of sample preparation.

Abstract: The microstructure of high Cr-containing directionally solidified Ni-based superalloys with different Re content were observed by scanning electron microscope. The segregation of alloying elements was also investigated by electron microprobe. According to the observation, the microstructure of as-cast samples included γ, γ', MC carbides and few (γ + γ') eutectic while that of heat-treated samples consists of γ, γ', MC carbides, M₂₃C₆ carbides and Re-containing carbides. With the addition of Re, some conclusions can be made as follows: Re exhibits the strongest degree of segregation to dendrite region and the segregation of Ti, Ta, Al become more serious. The γ' phase of as-cast samples is butterfly-like. For heat-treated samples, the γ' phase evolves from sphere to cube, the size of the γ' phase in the dendrite region decreases from 464 nm to 235 nm while the volume fraction of them barely changes.

Abstract: The macroporous resin is one kind of new non-ionic organic high polymer absorbent with nearly 20 years development. It takes the styrene and the acrylic ester as the monomer, divinyl benzene as the crosslinking agent, the toluene and the xylene as aperture reagents. They intersectantly linked the polymerization to form the porous skeleton structure mutually. This experiment is the utilization of aerosol polymerization method in preparation of rhenium concerned polymeric adsorbent. On research of monomer and crosslinking agent allocated proportion, dispersing agent amount used, temperature and mixing speed control, the different monomer and the crosslinking agent separately affected the synthesis different macroporous polymeric adsorbent. Also we investigated the adsorption performance quality of the different macroporous polymeric adsorbent in order to make the best particle size.

Abstract: Nowadays the actual problem of geochemistry is a deep and complex processing of mineral raw materials. Data on the quantitative content of precious and rare metals in various types of ores and rocks are necessary. It stimulates the development and improvement of chemical analytical methods for determination of these elements. Such methods are not applicable without sample preparation stage. Preparation of samples for analysis is the decomposition and preconcentration of rare and precious metals from matrix of mineral raw materials. The sample preparation schemes of platinum, palladium and rhenium are described in this paper.

Abstract: Ir-Re alloys were synthesized from nanocrystalline iridium and rhenium powders under high pressure (4 GPa) und temperature (2000° C). They were characterized using powder X-ray diffraction and scanning electron microscopy.

Abstract: Measurement results of the research aimed at plasma spheroidization of a mixture of W-re powders are presented in the paper. Such powders may be a good prefabricated unit for production of W-Re sinters or materials comprising, besides W-Re, also other metals like Fe, Ni, Co, and so on. The influence of plasma spheroidization parameters on the powder oxidization level, and the process effectiveness are shown. Moreover, measurement results of powders oxides reduction after plasma modification are presented.

Abstract: Measurement results of 92W-5Re-3Ni and 77W-20Re-3Ni sinters produced from powders spheroidized in a plasma jet are presented in the paper. The production process is described, typical microstructures are presented, and the analysis of chemical composition in selected microregions of the samples have been performed. Additionally, a comparison of selected properties of materials produced from powders spheroidized in plasma and from non-modified powders is shown.