Synthesis of nanocrystalline solid solutions based on zirconia and hafnia

Nanosized (2–8 nm) amorphous powders of the solid solution based on zirconia and hafnia are synthesized through back coprecipitation upon treatment of gels at temperatures from +20 to −77°C. Heat treatment of these powders at temperatures up to 1000 and above 1100°C leads to the formation of cubic (fluorite type, O _h ⁵ = Fm3m) and tetragonal phases of the Zr₈₂Hf₁₀Y₃Ce₅O _x composition, respectively. It is revealed that a decrease in the synthesis temperature (from +20°C to −6°C) results in a decrease in the size of gel agglomerates from 30 to 1 μm. Recrystallization processes in the gels prepared using cryochemical treatment are developed very slowly in the temperature range 500–1200°C (the crystallite size does not exceed 25 nm). Original Russian Text ? T.I. Panova, V.B. Glushkova, A.E. Lapshin, 2008, published in Fizika i Khimiya Stekla.     

A Study of the Dust Collection Process in the Production of Refractories

An experimental setup for studying filter-assisted dust collection is described. The role of various factors — hydraulic resistance, filtering velocity, dust concentration, pressure drop, efficiency of recovery — in the performance of filters intended for use in the production of refractory materials is considered. The dust removal method was tested under industrial conditions at the Semilukskii Refractory Plant and can be recommended for wider use in different branches of industry.     

Selection of Polyacrylonitrile Fibre Modification Parameters

The studies conducted show that: the efficiency of modification of as-spun PAN fibre is higher than with modification of the conditioned fibre; the fibres obtained can be recommended for fabrication of fire-resistant fabrics for work clothing.     

Vibrational-shock surface cleaning

Formulas are presented for the stress arising in a vibrational-shock tool and at the surface of the treated object (a pipe, say), the coefficient of impact-energy transfer to the object, the depth of residual plastic deformation at the object??s surface, and the stress in the deposit at the object??s inner surface. A sample calculation is outlined.     

Spectrophotometric Study of Interaction with Water of Barley Seeds after Their Colloid Treatment in Silica Sols with γ-Fe2O3 Nanopowders

Glass Physics and Chemistry - It is shown that the deposition of silica sol shells on the surface of barley seeds based on hydrolyzed tetraethoxysilane with the addition of γ-Fe2O3 (maghemite)...     

Effect of the modification of barium titanate on the permittivity of its composites with cyanoethyl ester of polyvinyl alcohol

The effect of chemical modification of submicron barium titanate particles by the deposition of M _x O _y (x = Ti, Co, Ni) oxide layers from aqueous solutions of the corresponding precursors is studied upon the surface properties of modified BaTiO₃ particles and dielectric permittivity of organo-inorganic composites obtained by their dispersion in the matrix of cyanoethyl ester of polyvinyl alcohol and useful in electroluminescent light sources. It is shown that a significant increase (by about 25%) of the dielectric permittivity is observed only when adding Nb₂O₅, in comparison with a similar composite which contains unmodified BaTiO₃. A correlation is found between the dielectric permittivity of the organo-inorganic composites and the presence of Brensted neutral and basic centers with pK _a = 6−13, localized on the surface of a filler, being capable of interacting with the polymer matrix. It is shown that an increase of the dielectric permittivity upon deposition of niobium oxide on the surface of BaTiO₃ is caused by formation of such centers and modification of the surface layer structure of BaTiO₃ particles, with transformation of rutile-like Ti-O bonds to anataselike ones.     

Geoceramic Matrices for Immobilization of Nonpartitioned Radioactive Wastes

Immobilization of radioactive wastes (RW) containing large amounts of process alkalis in ceramic matrices based on acid and basic rocks is studied. Immobilizing characteristics of samples with an RW content of 15% are obtained. The best geoceramic matrices are characterized by the forward leaching rates with double-distilled water of 1 × 10^{- 4} and 1 × 10^{- 5} g cm^{- 2} day^{- 1} for Sr and Cs, respectively, and the steady-state leaching rate of about 2 × 10^{- 6} g cm^{- 2} day^{- 1}. Possible fixation mechanisms of the radionuclides in the matrices studied are discussed. Comparative analysis of properties of the geoceramic matrices and borosilicate and some other existing matrices for RW immobilization makes it possible to recommend some kinds of the geoceramics as matrices for immobilization of nonfractionated intermediate- and high-level radioactive wastes.     

Modification of synthetic materials to reduce combustibility

The studies conducted demonstrated the effectiveness of using Phosdiol for reducing the combustibility of PE fibres and the small effect of PAN and PA fibre fire barriers. The oxygen index of flameproof fibrous polyester material was 27.5%, which allows assigning it to difficultly combustible polymers, and the strength of the fibre increases by 12–15%. __________ Translated from Khimicheskie Volokna, No. 1, pp. 35–38, January–February, 2006.