The thermodynamic properties of Ln2BaO4 (Ln = Sm, Dy, Ho)

The thermodynamic properties of the Ln₂BaO₄ phases (Ln = Dy, Ho, Sm) were studied by the electromotive force method with a fluoride electrolyte (890–1180 K), solution calorimetry in 1.07 N hydrochloric acid at 298.15 K, and differential scanning calorimetry (298–860 K). The experimental data were jointly processed, and the thermodynamic functions of the compounds over the temperature range 298–1200 K were calculated.     

Redispersion of Highly Disperse Powder of Titanium Dioxide in Aqueous Medium

Based on an analysis of interparticle interaction in highly disperse powders, a parameter is suggested allowing one to evaluate the tendency of dispersed particles to the formation of aggregates, the aggregation coefficient. It was shown that the particles of metal oxide powders with radius smaller than 10 m are present in their aggregated state. It was found that redispersion of highly disperse titanium dioxide powder in the aqueous medium is incomplete. The incomplete redispersion may be caused by the roughness of particles and/or the formation of the regions of entrapped air that are not destroyed by capillary pressure.     

Behavior of Cross-Linked Copolymers of Acrylic Acid and 5-Vinyltetrazole in Aqueous Media

The equilibrium swelling of new hydrogels based on sodium acrylate and N,N-methylenebisacryl- amide modified with 5-vinyltetrazole in water and aqueous solutions of nickel salts in the stage of radical polymerization was studied. The influence of 5-vinyltetrazole concentration in the monomer mixture on the characteristics of the resulting copolymers was studied.     

The ortho effect in the mass spectra of ortho/para isomers of bisphenol a derivatives and related compounds

New examples of the ortho effect in bisphenol A derivatives including interaction of the hydrogen of the ortho-hydroxy group with the neighbouring aromatic ring have been observed. The characteristic ions [M ? PhOH]^+middot; (m/z = 134) and [M ? CH₃ ? PhOH]⁺ (m/z = 119) were shown to form through the hydrogen transfer from hydroxy and isopropyl groups, respectively. The spectra of cyclic derivatives having ortho-hydroxy functions show [M ? 43]⁺, [M ? C₈H₉O]⁺, m/z = 147, m/z = 135 and [M ? C₉H₁₀O]⁺ ions. The proposed mechanims of the corresponding transformations were supported by mass spectra of deuterated analogues, methyl and trimethyl silyl ethers.     

Heterocyclic nitro compounds

Ketones of the 3-nitro-5-R-1,2,4-triazole series react with hydrazoic acid in concentrated sulfuric acid to give triazolyl-substituted acetamides. Acid hydrolysis of the latter leads to 1-aminoalkyl-3-nitro-5-R-1,2,4-triazoles. Intramolecular cyclization with the elimination of HNO₂ and the formation of 2-nitro-5,6-dihydro-1H-imidazo[2,3-b]-1,2,4-triazole was noted in the case of 1-(2-aminoethyl)-3,5-dinitro-1,2,4-triazole.See [1] for communication XX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1271–1273, September, 1977.     

Two-component magnetization in Pd<Subscript>99</Subscript>Fe<Subscript>01</Subscript> thin films

Magnetometry data on 5- to 40-nm-thick PdFe films are presented for the first time. It is found that the decrease in the film thickness leads not only to the lowering of the temperature of the transition from the paramagnetic to ferromagnetic state and to the decrease in the saturation magnetization but also to the drastic changes in the film properties. In particular, the type of the temperature dependence of magnetization changes, the Curie temperature becomes strongly dependent on the applied magnetic field, and two transition temperatures are observed in zero magnetic field. The observed effects are attributed to the transition from the three-dimensional distribution of ferromagnetic clusters arising around impurity iron atoms to the two-dimensional one and can be treated within the model of impurity magnetism suggested by Korenblit and Shender.     

Sodium alginate and carbopol microcapsules: preparation,polyphenol encapsulation and release efficiency

Russian Chemical Bulletin - An approach for the preparation of a polymer delivery system consisting of sodium alginate (SA) and carbopol was developed. The efficiency of the inclusion of medicinal...     

Structural self-organization, domain structure, and magnetic characteristics of manganites of the La-Sr-Mn-Ti-Ni-O system

The structure and phase composition of La_0.65Sr_0.35Mn_{1 ? x ? y} Ni_xTi_yO₃ manganites (0 ≤ x ≤ 0.3; 0 ≤ x + y ≤ 0.3) obtained by solid-state reactions in air are studied by x-ray diffraction. All the samples are single-phase materials and have an orthorhombic or pseudocubic structure, depending on the chemical composition and the sintering temperature. The saturation magnetization and the temperature dependences of the magnetic susceptibility are measured. The magnetic structure of manganites is characterized by the existence of inhomogeneities in the form of ring domains or drops whose size is in the range 30–100 μm. A study of the surface by scanning tunneling microscopy reveals the occurrence of ring, spiral, or lamellar structures with a characteristic size of the order of 10 nm. A possible approach to the interpretation of the obtained experimental results based on the concept of self-organization processes leading to the segregation of ion pairs and the formation of elastic concentration domains is discussed.     

Asymmetry in the dynamics of domain walls in thin exchange-coupled ferromagnetic films

The kinetics of remagnetization after magnetic field switching was studied by the magneto-optic visualization technique in the bilayer hybrid structure composed of exchange-coupled FeNi and FeMn films. It was observed that not only the static but the dynamic characteristics of remagnetization as well depend on the polarity of a field applied along the direction of easy magnetization. The rate of the process was found to be exponentially dependent on the field strength in both directions, but the rate varied by factors of 10 upon inversion of the field. It was shown that this difference is the consequence of variation of both the time of domains nucleation and the velocity of domain walls motion.