Abstract: Composites with nano-SiO2 particles and high density polyethylene (HDPE) matrix were
produced by hot pressing with various particle contents and particle surface treatment using
commercially available silane coupling agents: γ-methacryloxypropyltrimethoxy silane and γ-
glycidyloxypropyltrimethoxysilane. The influence of the particle treatment on the mechanical
properties of composites was determined by compression and indentation tests. Additionally,
numerical analysis was performed in order to calculate Young’s modulus and stress concentrations
for various particle contents in order to provide reference data by simulating micro- and macro
particle composites with perfect bonding to the matrix.
Abstract: Poly(methylhydrosiloxane) [PMHS], prepared by siloxane equilibration reaction, was
used for the hydrosilylation with 1-decene to obtain poly(methyldecylsiloxane) [PMDS]. Pt(0)-1,3-
divinyltetramethyldisiloxane complex was used as a catalyst for hydrosilylation reaction. In order to
investigate the kinetics of the formation of PMDS, a series of experiments was performed at
different reaction temperatures (from 48 to 64 °C) with catalyst concentrations of 7.0 · 10-7 mol of
Pt per mol of CH=CH2. All reactions were carried out in bulk, with equimolar amounts of the
reacting Si-H and CH=CH2 groups. The course of the reactions was monitored by following the
disappearance of the Si-H bands by quantitative infrared spectroscopy. The obtained results show
that an induction period occurs at lower reaction temperatures and that the rate of Si-H conversion
follows the first-order kinetics.
Abstract: The aim of this contribution was to study the rubber elasticity of dry and swollen
networks obtained by cyclotrimerization crosslinking reaction of isocyanate groups located at a
linear telechelic network precursor. Telechelic diisocyanates were prepared in the undiluted state
from 2,4-tolylene diisocyanate, α,ω,dihydroxypoly(oxypropylenes) and different contents of the
monool component 2-(2-metoxyetoxy) ethanol. The network synthesis proceeded in a bulk.
Detailed network topology was calculated by the theory of branching processes. The equilibrium
swelling degree of prepared samples was related to the parameters, which are experimentally
accessible for a network arising from an end-linking process using the Flory-Rehner theory. The
experimental data for network modulus were compared with those arising from the "affine" model,
"phantom’ model" and the model of constrained junctions.
Abstract: Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been
widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma
irradiation has been successfully employed in the modification/sterilization of such porous
composites and that it has advantages over other procedures. In this study, differential scanning
calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass
transition behavior and structural relaxation, as well as to estimate the activation energy for this
process. The apparent activation energy ΔH* for structural relaxation in the glass transition region
was determined on the basis of the heating rate dependence of the glass transition temperature Tg.
Furthermore, the results were correlated with those obtained by gel permeation chromatography
(GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is
the main reason for the decrease of the glass transition temperature and/or activation energy with
the absorbed dose.
Abstract: New functional polymeric, semiconducting materials were synthesized by chemical
oxidative polymerization of acriflavine hydrochloride in aqueous solution at room temperature,
using ammonium peroxydisulfate as an oxidant. Polymerization products were characterized by gelpermeation
chromatography (GPC), FTIR spectroscopy, scanning electron microscopy (SEM) and
conductivity measurements. The influence of the oxidant/monomer molar ratio on the molecular
structure, molecular weight distribution and the electrical conductivity of polyacriflavines was
studied. Molecular weights approach a maximum value of ~20000. The polyacriflavine prepared by
using oxidant/monomer molar ratio 1.25 shows the conductivity of 2.8 × 10–7 S cm–1. New
substitution pattern shown by FTIR spectroscopic analysis combined with MNDO-PM3 semiempirical
quantum chemical calculations revealed N─C2 coupling reactions as dominant. The
formation of phenazine rings in ladder structured polymerization products was observed by FTIR
spectroscopy. The existence of a certain polyacriflavine crystalline structure was suggested from the
Abstract: Effects induced by uniaxial compression and external electric field in P2P to P6P
oligophenylene molecules are investigated by versatile calculations. In this way some useful
relations between particular values of compression or field directions and intensities to specific
changes in molecular structure and properties have been established, enabling estimation of
possibilities for tuning the materials characteristics and their spectroscopic analyses. The results are
compared to the existing experimental data and similar calculations, and some consequences for
applications of oligophenylenes-based materials are discussed.
Abstract: The paper reports on an experimental study of the Mode I interlaminar fracture of
unidirectional carbon fibers/epoxy resin composites. Mode I delamination strain energy release rate
GIC was determined in double cantilever beam (DCB) test, before and after gamma irradiation at
various doses. Glass transition temperature, Tg of epoxy matrix was determined from dynamic
mechanical measurements. The delamination surfaces of tested coupons were observed by scanning
electron microscopy. The variations in GIC values were correlated with irradiation doses, Tg values
and the features of delamination microfractographs, as well as with the variation under irradiation
of matrix or fibre/matrix dominated mechanical properties.
Abstract: The rods of Fe-based bulk metallic glasses with the nominal composition
Fe65.5Cr4Mo4Ga4P12C5B5.5 were cast by melt injection into 1.5 and 1.8 mm diameter copper molds.
The thermal stability, microstructure and crystallization behavior were investigated by differential
scanning calorimetry, optical micrography and X-ray diffraction, respectively. The wide
supercooled liquid region between crystallization temperature (Tx) and glass transition temperature
(Tg) in the as-cast state Tx=Tx-Tg=60 K, as well as the high value of reduced glass transition
temperature Trg=Tg/Tl=0.567 (Tl is liquidus temperature) approves enhanced thermal stability of the
alloy against crystallization. In the as-cast “XRD-amorphous” state, microhardness HV1=742 was
observed. Multistep current annealing thermal treatments were performed for structural relaxation.
After applying high enough heating power per square area (PS ≥ 6 W/cm2), intensive crystallization
of the samples characterized by appearance of several iron-metalloid compounds (Fe5C2, Fe3Ga4,
Fe63Mo37 and Mo12Fe22C10) was observed. The microstructure changes after crystallization bring
about differences in the microhardness values. The areas of still present amorphous matrix are with
increased value HV1=876, but a remarkable decrease to HV1=323 was observed in precipitated
crystallized zone that propagate along inner part of cylinders.
Abstract: Phase transformations and magnetic properties of multiphase Nd4.3Fe76.2B19.5 alloy were
investigated in the temperature range of heat treatment 600-700°C. The influence of different heat
treatment regimes was observed by correlation of phase composition and measured magnetic
properties. The heat treatment regime, which provided the microstructure that improves exchange
interactions between grains of soft and hard magnetic phases and consequently enhances magnetic
properties, was defined and discussed. For optimized magnetic alloy grain size of the present phases
Fe3B, Nd2Fe14B and α-Fe was calculated by size-strain analysis of X-ray powder diffraction data.
Calculated mean grain size was on a nanoscale, below 30 nm.
Abstract: The magnetoimpedance (MI) effect in magnetically soft Fe89.8Ni1.5Si5.2B3C0.5 metallic
glass ribbons is studied in this paper. As soft magnetic properties were determined by field induced
anisotropy (and therefore by magnetic domain structure), ribbon samples were annealed under
tensile stress in order to enhance induction of transverse anisotropy and to improve
magnetoimpedance effect. Stress-annealing (SA) technique up to 420 0C/475 MPa/30 min. was used
for tailoring electrical resistivity (ρ) and magnetic permeability (μ), i.e. two material properties that
in classical skin effect determine the penetration depth δm and therefore have influence on MIeffect.
The critical frequency of about 600 kHz was observed as the point with the initial increase of
MI. Significant improvement of MI-response reaching the value Z/Z ≈ 25 %, after annealing at
420 0C, was recorded at driving frequency 4 MHz. The highest MI-element sensitivity was found for
low magnetic field intensity where values of about 12 % / kA/m were attained.