Effect of Cr(III), Fe(III), Co(III), and Ni(II) acetylacetonates on the formation and thermal oxidative degradation of epoxy-anhydride polymers and composites

The effect of Cr(III), Fe(III), Co(III), and Ni(II) acetylacetonates on epoxy-anhydride polycondensation in preparation of unmodified polymeric materials based on UP-650T epoxy resin and isomethyltetrahydrophthalic anhydride and of epoxy-siloxane hybrid composites was examined The resistance of the materials obtained to high-temperature oxidation and thermal oxidative degradation was evaluated.     

Influence of zirconium dioxide nanopowders on thermal oxidative degradation of an epoxy polymer

The influence of zirconium dioxide nanopowders on the thermal oxidative degradation of an amine-cured epoxy polymer was studied.     

Shape memory effect in the epoxy polymer composites with aggregated filler

The specific features of the stress-induced shape memory effect are studied for composites based on various polymers and fillers, which can form aggregates and are capable of marked compaction. The appropriate deformation schemes make it possible to prepare composites with different structural states, which give various signs and ratios between longitudinal and transversal strains upon shape recovery. The criterion is proposed for estimating the ability of the composite for shape recovery with marked volume changes: the relative density of the filler defined as the ratio of powder density and compacted powder density.     

Observation of radiation instabilities of a two-mode He-Ne laser with the help of interference of polarized rays

Instabilities in the operation of a two-mode He-Ne laser are observed with the help of interference of polarized beams. Two interference patterns created by two radiation modes alternatively appear. The contrast of the interference pattern increases under the action of an external constant magnetic field on the laser. If one of the interfering beams is delayed sufficiently long, the instability manifests itself in the motion of interference fringes in a direction that depends on which of the two beams is delayed. The particular features of the evolution of the interference pattern are explained based on interference equations for the two modes that take into account the orthogonality of the linear polarizations of the modes, as well as changes in their amplitudes and frequencies.     

Production of carbon-nitrogen coatings modified by titanium nitride

We offer a method of producing composite coatings based on carbon-nitrogen compounds modified by titanium nitride clusters. The structure of the material obtained is studied by transmission electron microscopy. A comparison between electron diffraction patterns from carbon-nitrogen and titanium-nitride modified coatings reveals the presence of a hexagonal syngony in the carbon-nitrogen condensate. The mech-anism of the modification effect on the structure and properties of the obtained coating is discussed.     

Mathematical model of the solid-phase extrusion of polymeric composite materials

A mathematical model of the deformation of a structurally inhomogeneous material in a conical die is developed. The model accounts for the possibility of the material's compaction and loosening during extrusion. It is demonstrated that both a monotonic decrease, and extremal variation in microporosity are possible with increasing degree of drawing, depending on the character of the composite and deforming tool. Computed results are compared with experimental data obtained for superhigh-molecular polyethylene-based composites filled by polymerization. Good correspondence is established between theory and experiment.Translated from Mekhanika Kompozitnyk Materialov. Vol. 31. No. 6. pp. 834–839. November–December, 1995.     

Composite film coatings prepared by cationic polymerization of epoxy-polysiloxane systems

Cationic polymerization of dicyclohexylpropane diglycidyl ether in the presence of boron trifluoride was studied with the aim to prepare hybrid coatings.     

Fused silica as a composite nanostructured material

A method for calculating the refractive index of optical fused silica by applying the model of effective permittivity of composite homogeneous media is proposed and realized. The calculation was performed using the tabular data of the refractive index of crystalline α quartz and the ratio of the quartz glass and α quartz densities. It was suggested that fused silica contains nanosized pores with a glass filling number q immersed in a matrix with a density differing from the α quartz density by a factor of κ, where κ is slightly less than unity. It was established that the Maxwell-Garnett model makes it possible to calculate the refractive index of quartz glass and its dispersion in the transparency range (404 nm ≤ λ ≤ 671 nm) with a deviation less than 0.0002 from the tabular values. The calculated and experimental values coincide at q = 0.155 and κ = 0.986.     

Peculiarities of spontaneous grating generation in light-sensitive waveguide layers during holographic grating formation

The generation of spontaneous (noise) gratings during the simultaneous formation of a holographic grating in thin (on the order of the cutoff thickness of the TE₀ waveguide mode) AgCl-Ag films by two laser beams with λ = 532 nm and polarization vectors that make an angle of 45° with the plane of incidence have been studied. The electron microscopy images and diffraction patterns have revealed a significant difference of the spontaneous-grating structure from the structure obtained under irradiation by one laser beam. The spontaneous gratings have a significant spread in the directions of their wave vector, and the diffraction pattern (recorded using a probe beam with λ = 337 nm) has the form of a bundle of diverging arcs that intersect at one point. This difference is caused by self-diffraction from the holographic grating, which is responsible for the main diffraction peaks with odd orders, the growth of spontaneous gratings because of the interference of the beams diffracted by the holographic grating with the waveguide TE₀ modes scattered in the film, and silver transport to the interference minima. The diffraction patterns are quantitatively analyzed and the period of the new (formed under two-beam irradiation) spontaneous gratings is calculated. The calculation results are in good agreement with the experimental data.