I. A. Martynova

Customised 2G HTS wire for applications

Reproducibility of superconducting properties and suitability for specific applications by means of customised finish are two important attributes required from commercial 2G HTS wire. This paper reviews the consistent performance of SuperOx production 2G HTS wire and describes two novel customisation options: surround polyimide varnish insulation and composite bulk materials assembled with 2G HTS wires soldered together.

Mixed ligand acetate, propionate, and pivalate complexes of rare earth metals with monoethanolamine: A new approach to the synthesis, composition, structure, and use for the preparation of oxide materials

Compositions of mixed ligand acetate, propionate, and pivalate complexes of rare earth metals of the cerium and yttrium groups with monoethanolamine are predetermined by the synthesis conditions and the nature of the carboxylate ligand and rare earth metal ion. Solid mixed ligand complexes [Ln(Piv)5(MEAH)][MEAH] and [Ln(Piv)3(MEA)], homoligand complexes [Ln(Piv)3] (HPiv is 2,2-dimethylpropionic (pivalic) acid), and gel-like hydroxo complexes [Ln(Carb)3–x–y(NO3)x-(OH)y(MEA)w(H2O)z] (HCarb is acetic (HAc) or propionic (HProp) acid) are isolated using original synthesis procedures involving ion pairs [MEAH]+[Carb]– (MEA is monoethanolamine). The compounds are studied by IR spectroscopy, 1H NMR spectroscopy, elemental and thermal analyses, and mass spectrometry. Specific features for the complex formation of rare earth metal pivalates with MEA are additionally studied using quantum-chemical simulation.

Yttrium tris-propionate monohydrate: Synthesis, crystal structure, and thermal stability

The complex [Y(Prop)3(H2O)]∞ (I) was prepared by treating yttrium carbonate, acetate, or acetylacetonate hydrates with propionic acid and characterized by the data of elemental analysis, IR spectroscopy, X-ray diffraction, and thermal analysis in air. Complex I has a polymeric layered structure with clear-cut structure-forming dimeric groups bridged by bidentate ligands. Only van der Waals interactions occur between the adjacent polymeric layers. In air, yttrium propionate monohydrate I is completely converted to the oxide at 600°C.

Chemical deposition of smooth nanocrystalline Y2O3 films from solutions of metal-organic precursors

A series of (Y(AcO)3·4H2O—Q—Solv) solutions (Q is monoethanolamine (MEA), diethanolamine (DEA), en, dien; Solv = MeOH, EtOH, PriOH, BuOH) was studied to choose the metal-organic precursor for surface smoothing treatment of metallic tapes by chemical deposition of nanocrystalline yttria films. Based on the results of viscosity, wetting angle, and thermal stability measurements, a solution (Y(AcO)3·4H2O—dien—PriOH) was proposed as a new metal-organic precursor. After chemical deposition of nanocrystalline yttria films about 300 nm thick on a Hastelloy C-276 metallic tape the surface roughness was reduced by a factor of 11 (from 9.0 to 0.8 nm on a surface area of 5×5 μm2).

Aluminum hydroxocarboxylates in solution deposition of planarization alumina films

Aluminum hydroxocarboxylates derived from butyric, pivalic, valeric, and isovaleric acids were synthesized and characterized. The synthesized hydroxocarboxylates were suspended in isopropanol and reacted with diethylenetriamine and monoethanolamine, which acted as hydrolyzing and complex-forming agents, to obtain precursor solutions for chemical deposition of smooth amorphous alumina films on metal substrates.

Insulation effect on thermal stability of Coated Conductors wires in liquid nitrogen

Superconducting wires are not perfectly homogeneous in term of critical current as well as stabilization. In resistive fault current limiter applications this could lead to hot spots if the fault current is only slightly above the nominal current of the device. Increasing stabilization by using thicker silver coating for example may prevent this problem but this method implies longer wire length to maintain the same impedance during a fault. Very efficient cooling in another way to prevent hot spots, this can be achieved in nucleate boiling regime. Optimal insulation can be used to prevent film boiling regime, staying in nucleate boiling regime in a much broader temperature range. In this work a novel technique is used to monitor in real time the temperature of the wire during the quench. Using this method several increasing insulation thicknesses are tested, measuring for each the heat exchange rate to the nitrogen bath. Exchange rate measurements are made in quasistatic regime and during the re-cooling of the wire. SuperOx wires provided with different insulation thicknesses exhibit an excellent stability, far above a bare wire. On the other side, for very thick insulations the stability gain is lost. Re-cooling speeds dependency on insulation thicknesses is measured too.

Interaction features of cerium (III) and europium (III) acetate and pivalate with monoethanolamine

The composition of mixed-ligand complexes of cerium (III) and europium (III) acetates and pivalates with monoethanolamine (MEA) depends on the synthesis conditions and the nature of carboxylate ligand. We prepared solid complexes [Ln(Piv)3(MEA)x], where Ln = Ce, Eu; HPiv-2,2-dimethylpropionic (pivalic) acid; x = 1, 1.5, and gel-like hydroxocomplexes [Ln(Carb)n − x − y,(NO3)x(OH)y(MEA)w(H2O)z], where Ln = Ce, n = 4; Ln = Eu, n = 3; HCarb is acetic acid (HAcet) or HPiv. The values of the coefficients x, y, w, and z depend on the synthesis conditions and heat treatment. Prepared compounds were characterized by IR and 1H NMR spectroscopies, elemental and thermal analyses, and MALDI-MS. The ESI-MS method was used to characterize the processes occurring in the solutions.