Formation of niobium boride from NB2O5 and boron with plasma arc

When a mixture of Nb₂O₅ and boron is heated to about 3000°C and subsequently annealed at about 2000°C in an argon plasma arc, NbB₂ is obtained. The products are found to be superconductors, theT _cof which is higher than 4 K. Some properties of the products, such as Vickers hardness and density, are comparable with those of NbB₂ prepared from niobium and boron. In the reaction forming NbB₂, a white powder is also obtained. The powder is identified as H₃BO₃ and is formed by the reaction between BO and water in the atmosphere. Therefore, the reaction of NbB₂ formation can be written as Nb₂O₅+9B=2NbB₂+5BO.     

Formation of Copper(II) Thiocyanato and Cadmium(II) Iodo Complexes in Micelles of Nonionic Surfactants with Varying Poly(ethylene oxide) Chain Lengths

Formation of copper(II) thiocyanato and cadminum(II) iodo complexes in micelles of poly(ethylene oxide) (PEO)-type nonionic surfactants with varying PEO chain lengths of 9.5 (Triton X-100), 30 (Triton X-305), and 40 (Triton X-405) has been studied by titration spectrophotometry and calorimetry at 298 K. In a given surfactant solution, all data obtained were analyzed by assuming formation of ternary complexes MX(n)Y(m)((2-n)+) (M = Cu(II),Cd(II); X = SCN(-), I(-); Y = surfactant), and the complexes thus form in aqueous phase (m = 0) or in micelles (m = 1). In the Cu(II)-SCN(-) system, spectrophotometric data obtained by varying concentrations of the surfactant can be explained well in terms of formation of Cu(NCS)(2)Y in micelles and Cu(NCS)(+) and Cu(NCS)(2) in an aqueous phase, and it turned out that formation constant of Cu(NCS)(2)Y increases with increasing PEO chain length. In the Cd(II)-I(-) system, the formation of CdI(3)Y(-) and CdI(4)Y(2-) is concluded in micelles, and that of CdI(+), CdI(3)(-), and CdI(4)(2-) in an aqueous phase. Interestingly, formation enthalpies of CdI(3)Y(-) and CdI(4)Y(2-) become significantly less negative with increasing PEO chain length. This suggests that transfer of the complexes from aqueous solution to a hydrophobic octylphenyl (OP) moiety in micelles is significantly more exothermic than that to a hydrophilic PEO one. Thermodynamic parameters of transfer of CdI(3)(-) and CdI(4)(2-) from aqueous solution to the OP and PEO moieties of micelles have been evaluated. Copyright 2000 Academic Press.     

Thermodynamic Aspects of Metal–Ion Complexation in the Structured Solvent, <Emphasis Type="Italic">N</Emphasis>-Methylformamide

Chloride complexation of cobalt(II), nickel(II) and zinc(II) ions has been studied by calorimetry and spectrophotometry in N-methylformamide (NMF) containing 1.0 mol-dm^{− 3} (n-C₄H₉)₄NClO₄ as an ionic medium at 298 K. A series of mononuclear complexes, MCl_n^{(2 -n) +} (M=Co, Ni and Zn) with n = 1, 3 and 4 for cobalt(II), n = 1 for nickel(II), and n = 1–4 for zinc(II), are formed and their formation constants, enthalpies and entropies were obtained. It revealed that complexation is suppressed significantly in NMF relative to that in N,N-dimethylformamide (DMF) in all metal systems examined. The suppressed complexation in NMF is mainly ascribed to the smaller formation entropies in NMF reflecting that the solvent–solvent interaction or solvent structure in the bulk NMF is much stronger than that in the bulk DMF. Formation entropies, Δ S₁^o, of the monochloro complex in DMF, dimethyl sulfoxide and NMF are well correlated with the Marcus’ solvent parameter, Δ Δ_v S^o/R, according to Δ S₁^o/R = aΔ Δ_v S^o/R+b. The a value is negative and similar in all metal systems examined, whereas the b value depends on the metal system. When a gaseous ion is introduced into a solvent, the ionic process of solvation is divided into two stages: the ion destroys the bulk solvent structure to isolate solvent molecules at the first stage and the ion then coordinates a part of isolated solvent molecules around it at the second stage. We propose that the a and b values may reflect the changes in the freedom of motion of solvent molecules at the first and second stages, respectively, of the ionic process of solvation.     

The passivation phenomenon of rhodium in fused lithium chloride + potassium chloride eutectic

The passivation phenomenon of rhodium was investigated in fused lithium chloride + potassium chloride eutectic by means of the potential sweep method. The current-potential curve obtained showed a typical N-shaped negative impedance. An anodic current rise was observed at +0.3 V vs. Ag/AgCl (0.1). The current was controlled by mass transfer and was ascribed to the dissolution of rhodium into rhodium(III) ions. The observed Flade potential was +0.45 V at 400°C. The passivation was found to occur due to the precipitation of supersaturated Rh(III) chloride onto the electrode surface. The residual current for the passivation was fairly high and the current increased significantly as the temperature was made higher. The dissolution current of rhodium into Rh(III) ions decreased with increase in the concentration of oxide ions. The fact revealed that the rhodium was passivated preferentially due to the formation of Rh(III) oxide. The residual current of the oxide passivation film was low enough. The thickness of the film corresponded to 10–20 atomic layers of the parent metal. Rhodium showed another anomalous passivation due to the formation of oxide. The oxide was formed at ?0.3 V and was reduced at ?0.6 V. It was considered to be a low valence rhodium oxide, RhO or Rh₂O. Rhodium was found to have a low chlorine overpotential. However, it was redissolved at the chlorine evolution region, above +1.25 V. The dissolution was not prevented even in the oxide ion containing melts.     

Intercalation compound of diclofenac sodium with layered inorganic compounds as a new drug material

The intercalation reaction of diclofenac sodium (DFS) with layered inorganic compounds, gamma-titanium phosphate (gamma-TiP), proton type titanium oxide (H-TiO2) and sodium type synthetic mica (Na-TSM), was examined on. The direct reaction of DFS in ethanol-water mixed solvent resulted in the large amount accommodation of DFS. The amount of intercalated DFS was the order of gamma-TiP>H-TiO2>Na-TSM corresponding to the order of acidity. The intercalation using phospholiopids was also examined to assist the intercalation reaction. However, the amount of intercalated DFS was rather small in comparison with those in the direct reaction. DFS accommodated in gamma-TiP dissolved into neutral and basic buffer solution stoichiometry while scarcely dissolved in the acidic solution. The mechanism of the intercalation and reverse dissolution was successfully accounted according to the ion-exchange mechanism between Na+ in DFS and H+ in gamma-TiP. The dissolution from tablet of DFS/gamma-TiP intercalation compound was examined by using a disintegrator. It was found that the dissolution rate appropriately controlled by mixing the disintegrator. The present results suggested the different possibilities in the clinical field to use layered inorganic compounds such as drug delivery system (DDS).     

Intercalation reaction of layered transition metal disulfides—II: Tetraalkylammonium hydroxide intercalates of 2H-tantalum and 2H-niobium disulfides

The intercalates of 2H-tantalum and 2H-niobium disulfides with tetraalkylammonium hydroxides were prepared in aqueous solutions. All intercalates prepared were hexagonal 2H-polytype, and their a-lattice parameters were similar to those of the original disulfides. The intercalates of both disulfides had similar c-lattice parameters, the values being 23Å in tetramethyl- and tetraethyl ammonium hydroxide intercalates, and 28Å in tetra-n-propyl- and tetra-n-butylammonium hydroxide intercalates, respectively. The increase in the c-lattice parameter was interpreted according to the effective ionic radii of tetraalkylammonium ions in aqueous solutions including alkali metal ions. It was found from this interpretation that the c-lattice parameter of the hydroxide intercalates increased stepwise at regular distances of 5Å corresponding to the increase in the effective ionic radius of the intercalated cations.     

Subfractionation of the dansylated derivatives of glucosyl galactosyl hydroxylysine by liquid chromatography and its application to a specific alpha-1,2-glucosidase assay

The dansyl derivative of glucosyl galactosyl hydroxylysine (GGH) was separated into two components, as GP-I (monodansyl GGH) and GP-II (didansyl GGH) by paper chromatography. GP-I was further fractionated into four peaks (a, b, c and d) by reversed-phase liquid chromatography. These peaks corresponded to the dansyl derivatives at the alpha-amino (a and b) and epsilon-amino (c and d) groups of their hydroxylysine residues. There is the possibility that the fractions for b and d are diastereoisomers of a and c, respectively, since the monodansyl derivative from human urine consists of a and c. GP-II was fractionated into two peaks, e and f, which may possibly be diastereoisomers of each other. Treatment of the a, b, c and d fractions with crude chicken liver enzyme resulted in the preferential cleavage of a and b and the production of monodansyl galactosyl hydroxylysine. Components c and d were also cleaved slowly, resulting in the production of monodansyl hydroxylysine by the successive action of beta-galactosidase on dansyl galactosyl hydroxylysine. The detected alpha-glucosidase activity was strongly inhibited by free mannosamine. The method developed using the monodansyl GGH fraction a (or b) and high-performance liquid chromatography facilitated the detection of alpha-1,2-glucosidase, which acts specifically toward GGH even in a crude enzyme preparation.     

Mössbauer spectra at 77 K of products formed during transformation of iron(II) hydroxide containing zinc(II) ion to Zn-bearing ferrite in aqueous suspension by air oxidation

At pH 7.0, lower crystalline iron (II) hydroxide, “green rust II” (the Fe^II:Fe^III mol ratios and the electron diffraction measurements do not indicate the tendency for Zn²⁺ ion to be incorporated in place of the Fe²⁺ ion) and Zn-bearing ferrite are formed from aqueous iron (II) hydroxide suspensions containing the zinc (II) ion at a Zn: Fe_tot. mol ratio of 1.00:2.00. At pH 9.0 and 10.0, higher and lower crystalline iron (II) hydroxides and Zn-bearing ferrite are formed. The ratios of higher to lower crystalline iron (II) hydroxide are approximately constant during oxidation at pH 9.0. The oxidation reactions are divided into two classes according to the Zn: Fe_tot. mol ratios. At pH 7.0, lower crystalline iron (II) hydroxide is formed at the early stages of oxidation and dissolved iron (II) species are formed during the oxidation at a Zn:Fe_tot. mol ratio of 0.20:2.80. Iron (II) hydroxide is formed during oxidation and dissolved iron (II) species are formed at an early stage of the oxidation at Zn:Fe_tot. mol ratios of 0.60:2.40 and higher. At pH 9.0 and 10.0, both higher and lower crystalline iron (II) hydroxides are formed at Zn: Fe_tot. mol ratios of 0.60:2.40 and higher, and 1.00:2.00, respectively. However, at a Zn:Fe_tot. mol ratio of 0.20:2.80, iron (II) hydroxide with a large quadrupole splitting value and dissolved iron (II) species with large isomer shifts and quadrupole splitting values are formed before and during oxidation at pH 7.0, and the formation of Zn-bearing ferrite is depressed (-FeO(OH) is formed) at pH 10.0.     

Excitation spectra of the intrinsic luminescence of solid neon

The excitation spectra are measured for the atomic and the hot molecular self-trapped exciton (STE) luminescence in solid Ne. The atomic STE component is enhanced in comparison with the molecular STE at 17 and 19 eV of excitation energies, which are located at the low energy side of the bulk exciton transitions. On the other hand, the branching ratio into the atomic and the hot molecular STE's is almost constant at the other excitation energies.     

Intercalation compounds of layered materials for drug delivery use. II. Diclofenac sodium

Intercalation compounds of ternary layered inorganic materials, synthetic mica (Na-TSM), with diclofenac sodium (DFS) and its drug release characteristics were investigated. Hygroscopic DFS was selected as a model drug to verify the anti-humidity and anti-oxidation of the intercalation compounds. Na-TSM powder was first mixed with the reduced-type phosphatidylcholine (H-PC) solution of chloroform or ethanol. DFS was then mixed with these solutions and heated at 37 degrees C to prepare the ternary Na-TSM/H-PC/DFS compound. A remarkable phenomenon was observed in the drug release study. The net amount of DFS from the DFS powder decreased apparently after 20 min arising from the decomposition of DFS in acidic medium. On the other hand, the net amount of the released DFS from the intercalation compound was invariant. Thermal analyses study indicated that DFS powder was hygroscopic and a significant endothermic peak was observed accompanied by a large weight loss due to the dehydration of adsorbed water from 40 to 90 degrees C. On the other hand, no significant dehydration reaction was observed in the intercalation compounds even in the sample stored under humid conditions. The present results indicated that the ternary intercalation compound was resistant to acid in addition to anti-humidity.