The potential of wastewaters from the galvanic industry treated to remove toxic heavy-metal contaminants for the manufacture of commercial products lies in the development of processes for their ...reuse. This research addresses the feasibility of employing galvanic waste in the production of powder coatings. Powder waste generated through the resource-saving ferritic method and electroerosion dispersion method is significantly safer for the environment than that generated through reagent methods. Coatings resulting from wastewater treatment exhibit mechanical properties that meet current industry standards. The introduction of 15 wt.% spent polyvalent iron oxide sorbent into paint coatings enhances their mechanical performances. Specifically, the rebound strength increases from 20 to 40 cm/kg and tensile strength from 5 to 7.4 mm, the bending strength decreases from 8 to 5 mm, and the corrosion resistance of the coatings improves by 1.5 times compared to the standard samples. These improvements are attributed to the introduction of chemically and thermally stable crystalline phases possessing ferromagnetic properties into the coatings. As a result, these coatings increase shielding against electromagnetic radiation in the megahertz range by three times compared to the standard coatings. A significant research finding is the potential for reusing ferromagnetic waste from the galvanic industry in specialized materials.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Measurements of the microwave surface impedance for high-temperature superconductor YBa
2
Cu
3
O
7−
x
(YBCO) films irradiated by 3 MeV Au
2+
ions at three irradiation doses (10
10
cm
−2
, 10
...11
cm
−2
, and 10
12
cm
−2
) were carried out at different temperatures (below the critical temperature of
T
с
≈ 90 К) and various rf current amplitudes by the use of the microstrip resonator technique. A noticeable decrease in the surface resistance and an enhancement of the linear response range at low temperatures were observed for moderately irradiated film exposed to an irradiation dose of 10
11
cm
−2
, while at higher irradiation doses (10
12
cm
−2
) an increase in the surface resistance and a decrease in the linear response range were observed for all temperatures below
T
c
. These results are discussed in the framework of phenomenological theory for the microwave response of superconductors with nano-sized structural defects.
The development of hydrogen energy and, in particular, high-performance submersible liquid hydrogen (LH) pumps requires superconducting bearings which can trap magnetic fields up to 1 T at 20 K. MgB ...2 is hence a promising candidate for this application. The superconducting properties and microstructure of differently prepared MgB 2 were compared and the ability of different composite materials to trap magnetic fields was studied. Hollow cylinders of the same geometry were manufactured from hot pressed (under 30 MPa) blocks prepared from Mg:2B with Ti, TiC and Ti-O additives as well as from melt-textured YBCO ceramics. The high critical current densities and critical magnetic fields should ensure high trapped fields in all these materials. Indeed all materials demonstrated the required performance; however, flux jumps are a serious issue in MgB 2 even in crack free cylinders and impeded higher trapped fields.
Improvement in the efficiency of diamond tools is inextricably linked with the use of high-strength heat-resistant diamond grains for tooling. Hence, study of the effect exerted by heat treatment on ...changes in the mechanical characteristics of diamonds produced in various growth systems is a relevant task. The effect of heat treatment (in an inert atmosphere) of diamond powders produced in growth systems using ferroalloys to dissolve carbon and promote the conversion of graphite into diamond on the mechanical characteristics of diamonds and elemental composition of inclusions formed on the crystal surfaces during heat treatment is examined. Following heat treatment in the range 700–1100°C, inclusions are observed on the crystal surfaces in diamonds produced in the Fe–Co–C and Fe–Ni–C growth systems. In our opinion, the effect results from ejection of the liquid metal phase to the surface by capillary forces. In crystals with a higher content of inclusions, the phenomenon of capillary ejection is manifested at lower temperatures than the melting of carbon solvent alloys in the diamond growth process. This is confirmed by a sharp change in the specific magnetic susceptibility shown by the samples with a high content of intracrystalline inclusions in the temperature range 400–800°C. For diamonds with a high content of intracrystalline inclusions, with increase in the heat treatment temperature in the range 700–1100°C, the precipitation of the solvent alloy on the surface of diamond crystals leads to crack generation and decreases the strength of diamond crystals. For diamond samples with a low content of inclusions, when the heat treatment temperature increases to 800°C, the specific magnetic susceptibility and strength hardly change (taking into account the relative error of the data obtained).
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The oxygen concentration and distribution in the microstructure of MgB 2 - and YBa 2 Cu 3 O 7-δ -based materials affect the formation of nanostructural defects and thus influence the critical current ...density, upper critical magnetic field and irreversibility field. For MgB 2 oxygen containing additions (Dy-O, Ti-O) in the form of nanograins occurred not to be very effective for an increase of critical current density, j c . Sn-O additions to MgB 2 can provoke even a significant decrease of j c due to a chemical interaction of Sn with MgB 2 . The processing pressure and temperature influence the defect density of the relevant pinning centers and the regularity of their distribution in doped and undoped MgB 2 as well as in MT-YBCO.
We study the influence of technological media of solid-oxide fuel cells on the mechanical and physical properties of Crofer JDA alloy and the materials based on the Ti
3
AlC
2
-type MAX-phase. It is ...shown that Ti
3
AlC
2
and Ti
3
AlC
2
–Nb materials with a porosity of 1% are comparable with Crofer JDA alloy by electric conductivity but possess higher strength and heat resistance than this alloy for lower density. These results enable us to recommend the investigated materials for manufacturing the interconnects of solid-oxide fuel cells.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We study the heat resistance and electric conductivity of the specimens of Crofer 22 APU steel, which is traditionally used for the production of interconnects of solid-oxide fuel cells, a bulk ...composite based on the Ti
2
AlC MAX phase, and a vacuum-arc coating of the Ti–Al–C system on a thin (0.5 mm) VT1-0 titanium sheet in the intact state and after long-term holding (1000 h) in air at 600°. We study the evolution of the phase compositions of the composite and the coating in the course of long-term holding in oxidizing media and the changes in the oxidation resistance and electric conductivity observed in the course of this evolution. It is shown that thin (0.5 mm) titanium interconnects with the indicated coating may serve as an efficient alternative to the interconnects made of the Crofer-type steel, which enables us to avoid the negative influence of chromium on the serviceability of solid-oxide fuel cells and significantly (by ~ 50%) decrease the weight of batteries of these cells.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The magnetic characteristics of iron oxide nanopowder (Fe
3
O
4
base phase) produced by electroerosion dispersion and consolidated at high pressures (2 GPa) and high temperatures (900, 1000, 1100, ...1200, and 1300°C) for 0.07 h in contact with hexagonal boron nitride were studied. The nanopowder was produced by dispersing iron granules or shavings in plasma induced at contact points between the granules when electric pulses of high current and voltage were passed through them. The metal granules being dispersed are in a constantly circulating liquid (water) atmosphere, creating a pseudo-boiling layer from the granules. The liquid (water in this case) cools the granules to prevent them from being welded and oxidizes the metal vapors that emerge in plasma, forming nanosized iron oxide grains carried by the liquid flow into sedimentation tanks (powders with different grain sizes sediment in different tanks). Room-temperature studies of the magnetic characteristics of samples consolidated from iron oxide powders showed that the materials sintered at 1200 and 1300°C were soft magnetics with virtually zero hysteresis. Their specific magnetic moments at 5000 Oe were 128.4 and 126.4 emu/g and the coercive force was negligibly small: 5.1 and 4.5 Oe. The materials sintered at 1100°C were characterized by a specific magnetic moment of 90.4 emu/g and a relatively low coercive force of 9.1 Oe. The specific magnetic moments of the samples sintered at 900 and 1000°C were significantly lower and the coercive force higher: 40.2 and 42.1 emu/g and 37.9 and 32.4 Oe, respectively. X-ray diffraction with Rietveld refinement revealed that the materials consolidated at 900 and 1000°C contained 75–80 wt.% FeO and 25–20 wt.% Fe, while the materials sintered at 1100°C contained, along with 32 wt.% FeO and 2 wt.% Fe, a significant amount of Fe
3
N (66 wt.%). The materials consolidated at 1200–1300°C contained 100% Fe
3
N phase. Hence, under high pressures and increasing sintering temperatures, iron oxides are reduced and then iron is nitrided with nitrogen released from boron nitride, which improves the soft magnetic characteristics of the sintered materials.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Comprehensive experimental results of fully oxidized (up to YBa2Cu3O6,9-7) melt-textured YBaCuO materials with different microstructures are presented. These microstructures are built respectively: ...(1) with a high dislocations density but almost without twins (after high temperature treatment at 2 GPa) and (2) with a high twin density, but practically free from dislocations and stacking faults (after high temperature oxygenation at 10-16 MPa). It is shown that for attaining high critical current densities and fields of irreversibility (jc(H||c, 0 T)=9·104 A/cm2, Hirr=9.7 T at 77 K), a high twin density in YBa2Cu3O6.9-7 matrix of MT-YBCO is required. The density of twins in fully oxidized materials depends on the distances between Y2BaCuO5 inclusions, larger twin densities are related to shorter distances between inclusions. The influence of phase composition of the initial powder mixtures on the distances between Y2BaCuO5 inclusions have been characterized and discussed.
The results of studying the thermal conductivity of hot-pressed AlB
12
–AlN ceramic composites with different AlN concentrations were presented. The thermal conductivity coefficient was measured for ...composite specimens at room temperature and approximated for AlB
12
.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
